My Barred Rocks have started loosing their feathers, mainly on their lower backs and now thinning on some of their necks. At first I thought my rooster was the cause because I have seen him peck at them in that area, and he is always going after them so I separated him for a while. Unfortunately, it has gotten worse and involving more chickens now. I don't see any mites or lice. Are they hard to spot? Could it be moulting? Noticed one of the hens sneezing a little yesterday, so I started her on Vet Rx. I have the BRs separated from my other 10 hens & 1 rooster for now. But I have no idea how to treat because I don't know what is wrong with them, and I'm getting nervous because it seems to be getting worse. A few seem to be loosing some weight, but they are eating and drinking okay. Any ideas???