You know, I had that happen one year.....I think over the winter when they're penned up more, they just get stir crazy and start pulling out eachother's feathers. A good idea is to just set a spell, and watch them....You might discover that one particular hen is doing the feather plucking.....a bully hen.
In my case, it was a pair of New Hampshire Reds that were pecking the crap out of everyone. So I rehomed them to a bigger farm.
Another thing to consider is lice. I never had lice until this winter. This is my third year with chickens, and I noticed some of the looked perfect, while others seemed very "scraggly" looking. My eyes aren't so great, but I managed to grab one up and look down into the feathers, and there were a few creepy-crawlies. I was so grossed out! But other BYC folks tell me that winter time is a common time for chickens to get lice. I didn't know that.
So I used seven dust--two applications and now no lice. A few of them still look kind of rough, but they should begin to improve with time.
Good luck! I hope you get things worked out,
Sharon
