Mites will remain in the wood, especially with the duct tape where they can hide. I would suggest that you remove the roosts on a nice sunny day, paint them with a couple good coats of kerosene and let them dry well in the sun before putting back in the coop. This will kill all the mites living in the wood and prevent their return. While they are drying, remove all bedding, wood chips, nesting materials and give the entire coop a good disinfecting while the girls are outside for the day.