My girls are 15 weeks old. I have three RIR and three BR. One of the rocks is definitely the bottom of the pecking order. I've never seen them hurt her at all. She gets a little peck now and again but never anything serious. Anyway, after being away for a couple days we returned today to find she is missing all but two of her tail feathers. Just the long ones. I am wondering if she might be molting (there are a good number of feathers in the coop/run. Or might the others be pulling them out?