I have a RIR hen doing this too and I'm at a loss. Two huge bald spots on her abdomen, one on her crop, big one on her back, wings look raggedy. I've been on bedrest and hadn't realized this was going on til now; she has been hiding when my teenager goes out to feed and clean up. Looks self...
Today I was given 7 new adult hens (buff Orpingtons and RI's). I was not expecting them to be in such terrible shape... the biggest one has pecked the rest nearly bald and when I put out food it was like piranhas on a steak. Feeling sorry for them, I put my own 4 BO's in their coop on the other...