I have about 30 - 40 chickens. over the past month or two, we have had three unexpected deaths. They all appear to be healthy and clear eyed. We do not see any evidence of any diseases. The three hens were all found in the coop, either in their nests, on in the middle of the coop sitting. There has been no evidence of a predator, no puncture wounds or lost feathers. We do not see anything swollen. They appeared to be fine prior to their untimely death. We are baffled, any help will be appreciated. thank you.