3 hens have died in the last 6 months. They look as through they are just resting/nesting but their head is down neatly in front of them, kind of like tucked under their feet. Different ages, different breeds. 1 in a dust bath spot, 1 on the floor of the coop overnight, 1 in the nesting box. I did have security footage of the one overnight and she just layed down and never got up again. No noise, no flapping, nothing. Any ideas? Could it be something they are eating in the yard free range? Maybe just natural causes? This is a total flock of 15.