Try an on site search on 'Pin Less Peepers'. Sometimes once the habit has been broken and feathers regrown they can be removed.
I am having a similar issue.
I have a flock of five hens - no roosters - my first flock. I first noticed the feather loss on one of my Black Austrolorps belly. Almost all of her feathers were gone. Then I noticed my other Austrolorp was missing feathers on her belly also. Then I started seeing feathers from the Rhode Island Reds around the run and coop (a little loss on their bellies but not nearly as much). I thought it must be mies or molting.
I inspected the birds I could catch - but couldn't find and signs of mites or lice on them. I did as some had suggested and went into the coop at night and rubbed a paper towel under the roost bars to see if any blood like smears appeared (a sign of red mites), but nothing. Just in case I removed all the old bedding out of their run and coop, sprayed everything down with mite spray and parasite spray (natural versions - not real strong), put DE everywhere and all new bedding. I did not treat the birds bodies directly.
They still keep losing feathers - all over now. Around the legs, head, neck, vent - but only one looked like her skin was slightly irritated. Many friends who have chickens thought they might be molting - but it is now over 4 weeks and I have seen no new feathers.
I read about depluming mites - which needs a skin scarping to see them under a microscope. So I took the worst off to the vet. She didn't find any evidence of mites, didn't think it was molting and thinks it is some allergic type reaction to the wood chips I am using (pine - no cedar). I don't think so though since they have had the same type and brand of bedding since I got them and the feather loss started before I changed out the most recent batch of bedding (so probably not a change in the pine chips).
They are 18 -19 months old now - so it is around the time they would molt the first time - but no new feathers yet has me doubting.
Frankly I am at a loss.
I did change their food from crumbles to pellets around the time they started losing feathers. Maybe they are not eating as much? The crumbles were 18% protein and the pellets are 16%. Just in case it is diet related my next step is I am going to give them some game bird feed mixed with their layer feed - to increase protein in case that is it. Also should help them when (fingers crossed) they start to regrow their feathers.
They are all basically laying as usual - although one started eating eggs about a week ago (related to feather loss?). They may have slowed down laying a little - but it has also been really hot.
Any suggestions are much appreciated!