Not going into coop anymore - new nesting boxes

[aart]

And this also explains why we're not seeing them on the chickens themselves.

You might see them on the birds at night, as roost mites hide during the day.
Treat the birds too.

 

[Briosafarm]

As others have said, DE does not work. Permethrin spray as has been suggested, or Elector PSP (active ingredient spinosad) is effective and approved for use in organic gardening.