I have eight hens who have lost the majority of their belly feathers and the feathers directly above their tails. This has been happening for the last two months. As of the last week they have reduced their drinking and eating. One hen just died randomly and appears to have not been pecked to death. Egg production has dropped. I used to extend their daylight with a lamp but quit three weeks ago. It's winter here in Maine and it has been below freezing for weeks. There is ventilation in their coop. Perhaps not enough. I use pine shavings. I provide Flocka block and scratch. A majority of the base of the deep bed method is frozen because of the temperatures so I cannot clean the coop completely. I am wondering if I have mites. I recently lost one hen who appeared to have a prolapsed vent. She bled on a another hen which I previously believed to be the cause of her death. Here are some photos can anyone help?