I have a water turtle that is about 3in and noticed a few days ago it has a dark very soft spot on the bottom of his shell that looks like its rotting like fruit its a light black color and very, very soft. I took him out of cage and put him in a tub with paper towels and been feeding him worms with calcium d3 powder on them. What could it be from? They have uva/uvb light its the tube style light and a nice basking area that stays around 86-88 and waters at 70-72. And is it ok to keep him in tub with damp paper towel on one side and dry on the other? Any help will be appreciated. Thanks
