I noticed that some of my 16 week old Sussex pullets have tail feather damage and even show a little blood where the feathers are missing I assume it's pecking order damage... they are in with about 10 older hens and a roo. They are cooped at night in a 4x4x8 coop and free range all day in a large fenced area that is about 30' x 250' of mixed area including blackberry brambles.... any suggestions?