I had a Buff Orpington die in her sleep last night. She was in the coop with the others (I have 5 others, all different breeds). There were no signs of disease on her and the others seem fine. The low here was 26 degrees, but it has been as low as 14 degrees. I do not use a heat lamp. The coop is enclosed and it is well ventilated. This is my first winter with them and I want to make sure the others are OK! Any thoughts?