Hello! Our chickens had some northern fowl mites. We tried various products including poultry shield, sevin dust, poultry dust, garlic, and others. We checked one of our hen's vent feathers and they are black from weeks ago when she had the mites. The thing is, the mites are not moving. Are they still alive? They have not been laying, but some aren't completely healthy and this is the 4th winter for others. Any advice would be appreciated. Thank you so much!