Help with feather loss

So I have 20 chickens total, 1 rooster and 19 hens. For a while, they had slowly been losing feathers mainly above their tails and a few on their bellies. I treated for mites (elector psp) a few weeks/maybe a month ago and they still look terrible.

The first pic is of the rooster’s back, who looks the worst (I know I know they look very bad). He is also being kind of a butthead lately and bullying the hens for some reason (chasing them around trying to mount but not even breeding them when he does, just standing on them for a few seconds). Not sure if this has anything to do with the feather loss? They have a good sized run and have access to all the feed and water they want. Egg production has been normal and even increasing.

I cleaned out the coop, sprayed EVERYTHING down with it generously, sprayed each chicken on the bare spots and under their wings. I’ve seen little starts of new feathers but they never go anywhere. Idk if they’re picking each other or what. Will it just take till their next molt to grow back or do I need to treat again? I also heavily spread diatomaceous earth everywhere. I’m not sure what the next step is. Any advice is appreciated TYIA