My favorite chicken Matylda, a polish chicken, died suddenly this morning. Our other chickens, a cochin and 2 hamburgs are fine. They were all apparently OK when I let them out of their coop this morning. I went out to refresh the water and she was laying on the ground dead without any sign of anything wrong. She was only 6 months old. We live in Vermont, so I have been concerned about cold, but today it's high 40s, sunny, windy. We added a reptile heat lamp to their coop a few weeks ago to add extra heat at night and it has stayed above freezing in the coop. They are usually outside almost all of the time during the day. I fed them some vegetable scraps this morning: beets, apples, cilantro stalk. I think these are all OK. Any ideas? We were going to add more polish chickens, but I'm not sure Vermont is the best environment for them, but then I don't know why she died...