I have 3 Mystery snails in my 20 long guppy fry grow out tank. Bare bottom with a mix of live and fake plants. I noticed on of their shells is peeling,cracked?? And the other has a brown streak now? I don't think it's the same issue but I'm not sure what's up? Is it a calcium issue for the peeling one(brown snail), and is the second one a bruise or is that poo(yellow one)?