Just a guess here...mine did this to some of mine and I started putting some can cat food that I get at Wal0mart and it seems that the feathers are a sign they need more protein and the cat food seemed to do it for mine. Its just a thought.. If chickens see a weak chicken they will peck it and in the end kill it so...mine get layer pellets and all the other things they need but they wanted meat so that is where the can cat food comes in and mine just love it...Just a thought to try..