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I do not think this is the result of a bully; feathers are missing in areas not normally plucked by a bully. I see many pin feathers/new feathers growing in on all but the black hen in the last picture. So whatever happened was a while ago. Check for parasites. Your chickens appear healthy. Since feathers are growing in I would not worry overly much. Do keep an eye on them.
I looked at her but didn't see anything parasite wise. What do you suggest for this? If mine, I would just observe. I would watch to see if there is another reason for the bare areas and to see if the patches soon fill in with new feathers. First time chicken owner so not sure - I use DM in their coop. I have poultry protector spray too. I will keep an eye on her. or rather them all.