The breast issue has me stumped. Do you suppose she could still be broody, and that is why she is pulling out her breast feathers? I saw her sister pull one of them out for her yesterday.
The other odd thing about the dark-combed girl is that she can be so broody, even when not sitting on a nest, that she sleeps right on top of her sister, and her sister allows it! One night I caught her standing on top of her sister in the coop! So I wondered whether she might just have a very hot breast from being terminally broody? She hasn't been on a nest since early June, though. Could a chicken stay broody?
She used to go under the hosue for only a few hours a day and then come out and sleep with her sister in the evening. We couldn't get under the house to her eggs to get them out. This went on several months until she went full-scale broody in early June. Her legs still have a bit of broody-girl orange in them.
Or could she have a fever from a disease and that is why she is pecking out her breast feathers, or is it most likely parasites? So hard to figure out, and I fear stressing her into a heart attack if I tried to take her to a vet, who is at a far distance (the avian specialist).
I will post a picture of her plucked out breast area.