Okay.
Are they bored? Do they have adequate room to roam? Do they have access to greens and things to amuse themselves with, like broccoli or cauliflower hung on a line for them to peck at? Do they need some calcium?
Sometimes chickens will eat feathers out of sheer boredom. Also chickens can start picking feathers off of each other in a form of cannibalism if they don't have enough room in their pen. The minimums recommended in the coop thread are just minimums. Most chickens do better with more room.
You might try to give them some protein booster. Young hens like yours are probably laying all winter and could use a bit of help. A handful of good high protein dry cat food once and a while is good as is the occasional scrambled egg. I give mine a bit of raw hamburger once every couple of weeks in the winter.
You could put some electrolytes and vitamin additives in their water to help with some Vitamin D which can be a problem in the winter. Just make sure you read the dilution directions carefully.
Good luck.
Mary