I have 23 chickens. 2 White Leghorn roosters. 1 White Leghorn hen, 2 Black Aussie hens, 1 mixed breed rooster and 19 Production Reds. These chickens have been outstanding all winter here in eastern Oklahoma. I have been getting 15 to 21 eggs each day all winter long. They are allowed free range during the day and have an enclosed coop to go into each night. My concern is on 1-28-2014 I found the White Leghorn hen lying almost frozen on the chicken coop floor. It was 5 degrees here that morning. After I brought her into the house she warmed up within a couple of hours but has never recovered enough to put her back with the flock. She eats and drinks well, has normal droppings but seems to suffer from vertigo. This morning (1-31-2014) one of the White Leghorn roosters was also having symptoms of vertigo. He was stumbling so much that he was easy for me to catch. I brought him into the house and put him into the cage with the white hen. He too eats and drinks well but is staggering around as if he is very dizzy. All the other chickens seem well at this moment. What do you think?