Are the lost feathers on the under side of the chicken? Sometimes broody hens will pluck out their own breast feathers to be able to get their skin onto the eggs to warm them more.
If the feathers are coming off from all over the chicken, they could be getting plucked out by other chickens during daily squabbles. If you have too many roosters and too few hens, they could be over mating the hens which can lead to them plucking the hens feathers out as they take turns holding them down to mount them. You have to watch them for a while and see what's happening.
They could be falling out on their own. Chickens molt this time of year (drop feathers to grow thicker ones for winter). It takes a lot of protein to grow out new feathers so their body will stop egg production until they are feathered out again. This is normal, though I've read that chickens don't always molt their first year. They will do it again in the spring to drop the heavy feathers, but it shouldn't be as noticeable as the fall/winter molt.