I have 6 chickens in my outdoor flock and 4 chicks inside. 3 of the older hens I got from a farm there about 1 1/2 yrs. old. they are bsl's and they were missing a lot of feathers when I got them due to being low on the pescing order and roosters being rough. I have had them for a year and two of them are still missing back feathers. I don't see any fighting so I am wondering if they will ever grow back? One of them is starting to lose festhers under her wings. The rest of the flock seems fine no problems eating or laying. Could only one chicken have mites or could there be another problem?