Sorry
@HappyFarmGirl but hemp bedding will not get rid of mites.
How to check for bugs below.
Many things can cause picking.
Like crowding.
Just Adopted 32 silk laced wyandottes, 3 roosters and 29 hens.
How big is your coop and run, in feet by feet?
Dimensions
and pics would be most helpful.
Also how old are these birds?....and....
Where in this world are you located?
Climate, and time of year, is almost always a factor.
Please add your general geographical location to your profile.
It's easy to do, (laptop version shown), then it's always there!
Bugs check
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).