I have 3 different breeds of chickens. I have cornish rocks, cochins, and welsummer chickens. They have all been raised together and are a couple of months old. Lately the Cornish rocks keep getting pecked and I have lost 2 hens already. Why have the other breeds just started doing this? They are only pecking at the Cornish rock chickens. I have 3 more hens that have sores and I have temporarily seperated them but can't for long. Is it because they are white or something else? I don't know what to do. Please help.