I have 8 pullets- 4 barred rocks and 4 reds. No roosters-never had any. Four of my birds have bald spots at base of tail. Fairly large-the size of a man's hand. I treat the spots often. This has persisted for 8 mos. I believe one of the reds is dominating and eating feathers. Problem is I don't know which one. Am I right in my guess and if so what can I do ? They get black sunflower seeds every day mixed in with their scratch.