If you're seeing a lot of new feathers laying around, that's what it is.
Old feathers lying around....
I'd guess picking/plucking, they like to eat those tender ones around the face and throat, and the bird being plucked doesn't seem to mind....SMH...have seen it often around here, especially on the EE's.
If it
is molting you should see new
pin feathers emerging there soon(tho those can be even
more delicious).
Have you checked them over real well for mites and/or lice?
Google images of lice/mites and their eggs before the inspection so you'll know what you're looking for.
Part the feathers right down to the skin around vent, head/neck and under wings.
Best done well after dark with a strong flashlight/headlight, easier to 'catch' bird and also to check for the mites that live in structure and only come out at night to feed off roosting birds.
Wipe a white paper towel along the underside of roost to look for red smears(smashed well fed mites).
If you do find bugs, permethrin dust or spray should take care of them.
'Night mites' will require the coop to be thoroughly treated with spray.
