I have 12 pullets and 1 roo. The Browns started missing saddle feathers and bottom feathers. I checked for mites and lice but, couldn't find any. I clean coop once a month and it was cleaning time. I did a complete (nest boxes and all) clean out and treated everything with poultry dust as I put it back together and bedded. Then I called the chickens in and did them. That was Sat. afternoon. Yesterday I checked and saw some pin feathers coming on the Browns. I thought good. Today when I fed their scratch I watched and saw some bare bottoms on the Blacks. They are being fed the high protein layer, grit, scratch mix (2 parts BOSS and 1 part cracked corn), and once in a while some left over macaroni or bread. And I feed back the egg shells for added calcium. I haven't noticed anyone pecking at the others and there are some feathers laying around. Any suggestions on what else to look for or what to do from here?