We were in the same position as you with the Red Mite. We have had our girls just over a year and absolutely no problems. Then Red Mites must have gone from one or two that we missed to zillions almost overnight.
They bite people as well so cover up (including hair - use a shower cap) and check yourself for mites after dealing with either the coop or the chooks.
At one point I put my bare arm in the coop to take out the perch and within minutes I had a clump of red mite attached to my arm covering about three inches diameter
![Sad :(](https://chat.allotment-garden.org/Smileys/green/sad.gif)
They were biting too and they left a light rash - awful critters.
We scrubbed out the whole coop four times in all with Jeyes Fluid and then soaked it with Poultry Shield. Then we grouted all the cracks and potential hidey holes and then painted the inside of the coop white so we could see what was happening better. Then we used Diatrom. Every day we cleaned out all bedding and re applied Diatrom (remember to use a mask and gloves).
Its been three/four weeks now and we are still getting a few mites each morning - but very few now. Its not fast
![Sad :(](https://chat.allotment-garden.org/Smileys/green/sad.gif)
Sadly we lost a chook to it too - our big Speckledy Doris just got too anemic to break back - despite all efforts :cry:
Feed your chooks extra spinach and other greens. Aunt Sally suggested a teaspoon of chopped liver a couple of times a week for a few weeks too. This seems to have helped the other two anyway.
Best of luck with it all. Its a sharp lesson and we will never neglect routine dusting again
![Sad :(](https://chat.allotment-garden.org/Smileys/green/sad.gif)