I went to the coop today to find one of barred rocks dead. They were all fine yesterday despite the cold. Had warm oatmeal in the am, fresh water, got the usual 12 eggs, I had 15 hens in all. They are locked up at nights and have a heat lamp. There was no indication any of them were sick. I see no blood or prolapse. What could it be? I am afraid for my remaining 14 hens.