ear mites

Help! I have done everything I can think of to help my small flock. All of the hens are shaking their heads constantly. Most of them have moderate to severe feather loss on their necks. I am guessing ear mites. I have cleaned the coop thoroughly, dusted them and even put ivermectin in their ears...

When I was closing up the coop this evening, I noticed that one of my hens (a 13 month old ISA Brown) was repeatedly yawning, shaking her head, and itching her head--pretty dramatically. She kept at it for a while. I just went back out to see if it has subsided but she was still intermittently...