So, I've caught one dying. The legs are splayed, as all the corpses have been. There was some rasping while breathing. But that dissipated. The chicken is just lying on its side, panting. She's willing to drink and otherwise doesn't appear distressed.
Thanks for responding.
I don't think it could be anything toxic. The coop is in an open front barn. We're way out in the country. Two sides of the coop are the sheet metal barn walls. The floor is small rocks coveted in hay.
It had been very hot for the last two deaths, but the previous...
I started with a group of 34 chickens, including three roosters, getting them from Ideal Poultry at one day old. I've lost some to fairly normal causes, but now, ten months in, I'm down to nine hens, though still three roosters, and the primary culprit (at least 12) is full grown, healthy birds...