I have 10 rhode Island reds with one rooster and 9 Hens. Recently we noticed that one of our hens wasmissing some of her tailfeathers. after observing for a while we noticed that the rooster seems to pluck them out. is this normal? It has become worse over time and now we are noticing taht some of the others are having their feathers plucked out. How do we stop this?