It sounds very much like he has the start of a shell fungus. If this is the case, you will have to clean the white spots with Betadine..then rince it off. Dry it with a clean paper towel, and put some antifungal cream on. I used Lotrimin antifungal cream. It has to have Clolrimazole 1% (for athlete's foot) Put her in a plastic tub under her lights and let her stay dry for a few hours before you put her in the water. If it spread any more ....take her to a Vet. Good luck.