This hen has had this issue now for a while. We kept thinking it was because she was pecked on by the others but now we are worried that is more than that. We have about 20 chickens in a very adequate space and most all of the others seem fine except for another with a bare behind and a couple with small bare spots on their backs just before the tail feathers. Wanting to see what yall have to say before treating. Thanks in advance for the info.