A friend of ours had a rooster that was fine and dandy..Then one day when she went to let chickens out of the coop, she noticed he had balance issues and would try to fly out of coop and land on his back. She said he seemed weak. Then she said when she would let them back in the coop, he was so weak she had to help him into it. After helping him she noticed mites crawling on her hand and they were all over his under feathers. She separated him from the hens immediatley and the next morning he was dead. Its winter time and she thought the bug infestation was weird since it was cold out. Then hens were unaffected. What caused all of this. She keeps a clean coop with plenty of fresh water and fresh food daily. We are all new to owning chickens as is she. Any advice?