Soft-shell turtles are very susceptible to shell rot and fungal infections on both plastron and carapace, especially in community settings indoors. Minor scratches turn into life threatening infections. If you buy a soft-shell turtle make sure its shell is flawless both top and bottom. Fighting the infections, once started, is very difficult and frustrating. Giving an injection to an unwilling soft-shell turtle redefines challenging.
Prevention is the key here.
We have found that sunshine, fresh air and space are the best preventatives. Wounds seem to heal themselves outdoors. I have seen soft-shell turtles continue to kill fish long after they have stopped eating, and just let the dead fish rot. The other remedy for soft-shell disagreements is enough space for the less dominant ones to escape. I worried that the concrete ponds would scratch their plastrons and that other turtle claws would scratch their carapaces.