Ok so, my flock of 6 chickens has been doing great. Since the weather has turned cold here in Michigan, some of the chickens have stopped laying eggs (which I hear is normal). This morning when I went to feed and water them, I noticed that one of the hens has some blood near her rear-end feathers...looked like she may have been pecked. Then I noticed another chicken's whole tail feathers are totally missing! Some of the others are looking a little bit shabby as well. My Isa Brown has a bare spot on her neck...no feathers at all. Quite a few feathers laying around the coop and pen. Should I be worried or is this normal 'moulting'?