We have 5 chickens in a decent sized coop in our backyard. They’re almost a year old and we noticed that their back end feathers were grayish in color and looked broken. I don’t think they are molting, and we scrubbed for mites or other bugs (Sevin, DE, etc) We live in Colorado and it’s been colder. We do occasionally put a heat lamp on if it’s in the teens, could this be affecting them? Today we noticed one with bloody feathers. Her quills seem to be intact but from what I’ve been reading, perhaps pecking? I have pictures attached. Any help or advice would be appreciated.