Do you think its feather mites?

[Bandit]

My SL Wyandotte has one wing that is looking raggedy and chewed, and also a few of the fluffy feathers underneath. And SOMEONE has really watery white diarrhea. I can't tell if it's her or not. Could she be molting just on one side or is it the mite thing? I don't know where she would get mites unless its from the little sparrows that sometimes eat the chicken feed. None of the other three have anything wrong that I can see. What do you think? And what should I do?