What do you do when your chickens start to lose all their feathers? Nothing, if it’s fall. They’re molting and look revolting. Nothing you can do about it.
Chickens grow a new set of feathers every year, usually in the fall, so they’re ready for cold weather. They can also molt in response to stress.
My older hens are in various stages of molt. Many of them are missing the feathers on their necks, others are missing wing and tail feathers, and a few over-achievers are missing both. In most cases, unsightly pinfeathers (the stubs of the new, emerging feathers) are making them look even worse.
Hens generally stop laying during the molt, which is why the fall is the worst season of the year for egg production. Winter is actually better, so long as you keep the water flowing and the feeders full and the hens aren’t exposed to too much wind or rain.
In the commercial confinement industry, the hens tend to get seriously overweight, and they lack the environmental cues that outdoor hens get, so their bodies tend not to realize that it’s molting season. Getting them back into trim sometimes requires that their water be withheld for several days and always requires that they be given little or no feed for up to two weeks. But we’ve never had these problems on free range.
Some people think you should feed hens extra-high protein diets during the molt, but I’ve never seen the point (or any research supporting it). A diet that will support high egg production will support high feather production.