And remember, the turtle may seem otherwise just fine, eat well, be very active, and still have shell rot, it doesn't seem to bother the turtle much. 

I have used one medicine to treat the badly damaged spots after the white materia has been removed. It's called Pevaryl and it is very effective against many kinds of fungus and bacteria. (The active ingredient is econazol and the manufacturer is Janssen-Cilag.) 

This turtle (in photos) got sick on June-July 1998. Now it has been almost 4 months and only now she seems better, the holes are healing over, but it will most likely take atleast two years, until the recovery is just about complete, the shell renews so slowly. Be patient. :) 

In this picture you can see a very sick little turtle. She has also other problems, but the well visible one is the skin problem. 

If your turtle keeps its eyes closed (all the time or most of the time) and seems languid (sleeps alot and doesn't move much around) and maybe refuses to eat, s/he may suffer of eye infection. 

Eye infection isn't a laughing matter either, because it seems to be the most common cause of death for young turtles! I know of experience. It is a very sneaky disease, it may at first leave unnoticed. It may progress very quickly, and if you suspect eye infection, you must start treating at once (either first yourself or go straight to the vet). If you don't treat it, the animal will probably die or atleast this may cause total blindness! It may also cause severe kidney damage. 

The most common reason for eye infection is lack of vitamin A in diet (the next most common is dirty environment). So the first thing to do is to give additional doze of vitamin A-supplement. If the condition isn't severe, I wouldn't recommend injection at first (especially if the turtle is small), because the amount of the vitamin is hard to estimate or count, when given to a small animal. So it may do more harm than help. Also the injection itself may be too much stress to a smaller turtle. There is also a very interesting article by Valerie Haecky that you might want to read: "Warning about vitamin A injections for swollen eyes."

You should also treat the eyes with either medicine you get from your vet, or with a solution, you can make yourself. Firts you must clean the eyes of any secretion you see. Then you can make a solution of distiled water and 3% boric acid or a solution of distiled water and salt. Drop a drop of the solution on the eye lid (you may use a cotton tip). Try to open the eye lid a little bit, so that the solution would at least partially go inside the lid. Do this twice a day for five days and remember to take care of the vitamin A in the diet.  If there is a very visible turn to worse overnight or if you see no improvments in five days, take the animal to a vet immediately. 

I have only one experience on spavins. Our "firstling" 
Konrad had a lump on his neck, right on front, near 
the bottom, where the neck skin and the shell join. 
It was maybe 15 mm wide and 5 mm high, pinkish. 
I only managed to notice it, because he was swimming 
and streched his neck to breath on surface. 

At first I was terrified and most worried I was if the lump 
would somehow prevent him from breething. Luckily no 
problems with breething, but he tried to scratch it, and it 
was so obviously itchy, so we decided to get rid of it 
(the lump, not the turtle). 

A successful treatment was Betadine-solution on the 
lump twice a day and once a day a local antiseptic 
Terra-Poly Vet (oxitetracycline). The lump was gone in 
a week, and in two weeks, there was no traces of the 
lump anymore. Also with this kind of diseases is always 
best to take the pet to see a vet, though the situation 
may not seem too severe, it might get serious in the long run. 

If there seems to be a white soft cover on your turtles shell, it might be fungus. The bigger the cottonish area, the more severe the situation, and the more advanced the disease. 

There could be one effective self-treatment, if the disease isn't very bad yet. Try to give the turtle salty baths daily. A teaspoon of salt to every four liters (a gallon) of water might be enough. The water should also be a bit warm, 26-29 degrees Celsius (80-85 Fahrenheit). The water should be deep enough to cover the shell mostly, but not really swim-deep. A bath for half an hour should be enough, maybe 45 min for the couple first days. Then let the animal airdry. Treat for few days, and if you see changes for better in a week, continue uptil 10 days (all together). If you see no improvements in a week, take the turtle to see a vetenarian. There is one medicine I know that is effective on many types of fungus and bacteria: Pevaryl (active ingredient is econazol and manufacturer Janssen-Cilag). 

The most common ways a turtle can get a cold are draught, too cold water or too cold air!

If there is whistling or wheezing sounds in breething or secretion from nose (the nostrils may be full of snot) or general lazyness or loss of apetite or the swimming position is unequal to either side, the turtle may have respitorial infection. 

The first I wanna say, that this if anything can be lethal in a short period of time!!! First you need to keep the animal warmer, water atleast 26 degrees Celsius (80 Fahrenheit) and the air also warmer. Then get the animal to a vet to get antibiotics and hope that they will work.     If not treated, the animal will suffer in vain and the expected life time will be four more weeks or less.

If your turtles shell gets soft (it should be firm and hard when pressured and you shouldn't be able to make a dent on it with the tip of your nail) and it bleaches from the edges, your turtle most probably has a soft shell. 

The reason for soft shell is lack of calsium. Either the diet doesn't include it enough or the animal cannot benefit from it. 

To benefit from the calsium in diet turtle needs to get D3-vitamin supplement or have a full spectrum light and vitamin A (better if both). The full UV light converts vitamin A into vitamin D3. The vitamin D3 makes possible the absorption of calsium in turtle's intestines. 

To treat your turtle give calsium and vitamin supplements and get a UV light (preferably the kind you can keep on 10-12 hours a day). If the condition has already got serious or there is no progress to be seen after a while, you better go see a vet immediately. 

It takes quite a long time to recover from this disease, and the marks of this condition are clearly visible on the shell for a long time or it may effect on the form of the shell. 

As been said, lack of calsium in diet can cause many problems: shell softening, weak bones, deformation of the shell. The symptoms in lack of vitamin D3, calsium and phosphor are pretty much alike. They all have a very important part in growing and regenerating of turtle's shell and bones and also general well-being. 

The calsium and phosphor needs to be in a correct balance in the diet so that the turtle would benefit of them. Then the vitamin D3 is been needed for the absorption of calsium in the intestents. 

You should provide your turtle additional calsium and vitamin D3 in supplements and also a fullspectrum light that will convert the vitamin A the turtle gets in diet to vitamin D3. But also remember, that these vitamins are lipsoluble and are dangerous if overdozed. So keep to the instructions in the supplement package! 

The most common consequence from lack of vitamin A is eye infection. Vitamin A is very important to the eyes and vision also in turtles aswell as in humans. 

To privent this condition add vitamin supplement to the food twice of once a week (depending on the supplement) accordingly to the instructions of the package. Do remember though, that vitamin A is lipsoluble and is dangerous if overdozed. So keep to the instructions in the supplement package! 

There are also some vegetables rick of vitamin A that you can include in the diet (tomatoes, carrots, spinach etc.) 

Comments: Vitamin K deficiency is almost always a result of long-term antibiotic therapy, which causes the destruction of the intestinal bacteria that synthesize vitamin K. Occasionally, it can occur without known cause. However, lack of vegetables might be cause. The usual symptom is bleeding of the gums. The treatment consists of giving the animal vitamin K and changing the diet to include more vegetable matter.