Hi everyone, I'm hoping to get some feedback. We live in Maine, have a relatively small flock of 12 hens, 1 rooster. During the winter, they stay in an "indoor" coop that's built into the end of the barn. It's insulated, but has 2 wall vents, a big vent on the door, and an access hatch out to a covered, screened-in outdoor area. We leave the access open all winter so they can come and go outside as they please. The birds don't seem sick. They're acting as normal, eating, vocal, etc. About 10 days ago, hubby went out for his morning visit and one of our oldest was dead. She was about 5 yrs old. No injuries, just dead. The next day, a chicken was missing. He checked the outdoor area and another older hen was lying under the ramp outdoors, dead. This morning, he found one of the young hens we got last year dead. Yesterday, she was fine. They have access to fresh water, food and we keep a heat lamp on for warmth and to keep the water from freezing. The coop is large, the floor is sand covered with a layer of straw that gets replaced frequently. It has been extremely cold here, and I'm wondering if that is the cause. We've kept chickens for about 5 years now, and while we've had chickens die for no apparent reason, it's been random and infrequent. Any advice would be appreciated!