Try to do everything on my list here as I have dealt extensively with the Northern Fowl Mite and hopefully this will work for you:
1. Make sure you are using something good. I use Eprinex too on occasion, but I don't depend on it entirely. So I am going to give advice that ignores Eprinex.
2. Dust chickens with poultry dust (permethrin) from feed store. Poultry science experts used to recommend Sevin garden dust and it worked really well for the bugs resistant to permethrin but unfortunately it is not approved for poultry use anymore.
3. Either spray the coop with permethrin liquid diluted as per label or dust coop with poultry dust (not DE) after tossing all bedding. Toss all nestbox material as well. If you don't toss nesting material they will be back.
4. Spray under roosts since you are dealing with red mites, and every crack in coop. I would recommend you go with permethrin liquid for this.
5. When you dust the chickens you might do as I do, and put dust in an old sock. I dust the vent area, under the wings, and everywhere but the face. I wear long sleeves, gloves, mask, and take shower afterwards.
6. Repeat all coop and bird treatments at 7 days. This is vital for mites.
7. Repeat all coop and bird treatments at 14 days. This is vital for lice, which has a longer life cycle.
If the repeat treatment is not done, or there is a reservoir left for the bugs, like a nestbox, they will be back.
Red mites can live with no poultry blood meal for 9 months.
Northern Fowl mites can live with no poultry blood meal for 3 weeks.
Lice die pretty quickly without poultry but I am not sure how long, and tend to stay mainly on the chickens from what I have read. I have not dealt with lice or the red mite but they will die if there is no reservoir left, the treatment you are using they are not resistant to, and the retreatments are done on time so that the life cycle is broken.