Mine, at that age, replaced a few feathers and grew new ones in. Pick up your babies and examine them one at a time carefully. (You should do this at least weekly anyway at this stage. We do it every other day.)
See if you find "pinfeathers", feathers in a casing, coming in. Those are their new feathers. If you find those coming in, likely they're growing new feathers and replacing old.
Also look very carefully at their feathers, their skin, under their down, under their wings, etc. Look for anything moving, or for l ittle white clusters of eggs anywhere on them. Look for redness around the vent, signs of broken off feathers, etc. (The feathers that you're finding - is the quill intact and empty at the end - no meat?) You're going to want to rule out mites and lice. Mites only come out at night, then sporadically, so take a few nights this week and go out and check then. Turn the lights on, but use a flashlight to really check them carefully. If you find mites or lice, post here in THIS thread and we'll tell you how to handle them. Some of us will be subscribed to this post looking for updates and waiting to help.
Also, what feed are you feeding them? Is it a good growing crumble for chicks with a good protein level? If you're feeding grain, is it less than 5% of their total diet? Do they get feed free-choice? Do you see any signs of fights, scrapes or sores? Any bald spots?
Also take a half hour and watch the babies. At about that age they start to pick at one another. That's about when I divide the smaller more delicate babies from the bigger ones or cockerels. Watch for bullying and feather plucking. You might want to have two grower areas.
I look forward to (both of) your replies.