I was wondering if this was normal with chickens. Not sure what could cause some of the feathers to appear missing but I also do not know if this means it's a problem or not. Attached are some photos of one of my chickens. I've looked at all of my other chickens double checking for this and they all seem to be fine except this one. Any idea if I should be concerned or not? This is on top of the chicken, more towards the front of the tail.