What size coop are they in or do they have space to spread out? Adding another food dish and water bowl might help if they are territorial over the food. A lot of times my flock fights because they are trying to eat at the same time. I have three food stations spread out with a lot of water.
All good questions. Age could be a factor so how old are they? Are you sure they are all girls? Where do you see this happening, is it just in the coop or also in the run? How big in feet is your coop? How big in feet is your run? Do they have access to the run if this is only happening in the coop? As Sourland asked, can you kind of describe what this pecking looks like?
they are just pulling feathers while they are dust bathing they will pick at the one that is bathing the run size is about 25 feet by 10 feet the coop is 3.5 ft x 4 ft there water is a 5 gal bucket with 4 nipples in it and the feed bucket is 5 gal and has two 3 inch openings I only have 3 birds and they are about a year and a half old they have a dust bath but will also dig holes in the sandy soil here in florida this is where I have notices most of the plucking going on itsa on there backs just above the tails and on there butts at first I thought it was mites but I cant see any I have dusted them with dimascious earth there health looks good and they act normal hope this helps
You shot down my theories. That is a lot of room for 3 chickens and in your weather they should be able to use all of it. At 1-1/2 years it is not a maturity issue. That doesn't sound aggressive at all, more like sociable grooming. Not that they should be grooming each other like that. I've seen that some and broke it up before it got out of hand. In those specific spots it should have nothing to do with molting.
How bad is the damage? Are they creating bald spots, photos might help? Are they eating the feathers they pull? What are you feeding them, protein level of their feed and how much and what other treats?
I got the run covered with wood chips I raise black soldier fly larva and they get it often along with scratch . I use purina laya feed and they have grit and oyster shell on the side I'll get some picks later today thanks all