This is my second hen to behave this way. I attributed the first hen's death to the heat. They both start out with an eye problem. One eye, shut all the time, pupil fully dilated. Eating good, then get lethargic. This is where the two diverge. Thought sour crop with the first (her crop was mushy and stank, did three flushes, treated with antibiotic and she seemed better), did well for one week, found her dead on the floor of the coop in the morning. I am concerned there is a disease, but not sure what and can't find anything in the books, taking them out. They free range in the yard, have free access to layena and a flock block, water in several areas, and electrolyte enriched water in one waterer. Weights are fine up until the very last. The first hen was a loner, two years of age. The second sometimes loner, three years of age. All from hatchery stock and vaccinated for Mareks. Any thoughts?