Both species are quite hardy once established and are not prone to shell rot at all. True, some arrive in the U.S. pretty beat up but shell rot occurs only in extreme cases.
Red cheeks in particular develope a very heavy,thick shell that is fairly resistant to rot.
Water conditions should be slightly acidic as this helps in preventing fungal problems with the skin. Hatchlings can get skin fungus if keep in dirty water that is too alkaline.