I've had luck with Exzolt and S76. You can by Exzolt at
https://pestiless.com/product/exzolt-50-ml-fluralaner/
It's not cheap, but it goes a ways.
I buy S76 from
https://ladygouldian.com/S76-air-sac-mite-treatment
Not really cheap either, if you dose 3 days one week-2 day the second week-1 day the 3rd week.
I also have 26 large chooks.
Though these were just tools in my toolbox. I had to scrub and clean the enclosure and coop every week for months and months before I won. To the extent of spraying rafters with diesel fuel, you name we did it. Even now I think I might be fighting them a bit, but I have a handle on what to do and execute quickly. I've had A LOT OF LUCK using First Saturday Lime with Neem POWDER and Captain Jack's Dead Bug (Spinosad) dust in their dust bath. It's my rooster, who just is a fricking magnet and does not dust bath as he should, lol. There are wild turkeys, geese, etc on our property constantly, so I guess it's just part of it. They free range. They snuck up on me last year and beforre I knew wth was gong on, I was infested. You can read some of my old posts. I thought going to have to "nuc" my house, my property, my animals and myself!
Disclosure... I did not have red mites. I do know I had, probably still have some NFM and I'm positive I had a depluming mite that burrowed, which is why the S76 really helped hit this from multiple fronts. My birds are very healthy and happy. I didn't lose any of them, though I think I was close.