@FunClucks Thanks for that! I think I will look for it when I get feed next time just to have on hand. I have read really good things about it. Maybe it will help the OPs hens too.
I don't have access to a chicken vet either so I totally understand. Sometimes we just have to do the best we can.
Eggcessive mentioned a product called Nustock it has Sulphur, pine oil and some mineral oil in it. I've not used it myself but have seen it recommended here for different...
I read this-
The mite burrows into the feather shafts and the skin surrounding the feathers. I googled 'depluming mites chickens' and clicked the image tab and found a few pics.
Also found this thread by @TwoCrows...
Have you researched Deplumming Mites?
https://tvmdl.tamu.edu/2020/10/05/depluming-mites-in-birds/
I have no experience with these but have seen posts here on BYC about them. This could be your birds issue. There are other sites online as well if you search. Also use the search feature here...