Less than 30 minutes ago I went out to my coop to let the chickens out, and one of my hens was laying face down by the door. I think she may have died very recently, maybe only an hour before I opened the coop, but I'm not sure. She showed no signs of being sick or acting ill the day before, and I couldn't find any wounds on her. She was a 1 year old Speckled Sussex. She had not been let out to free range for 6 days, so I don't think she could have gotten into anything to make her sick. She may have been egg-bound, but she laid an egg late in the day yesterday so I don't think that was the case, I could be wrong. The water dish and the food bowl was full so I don't think she died of hunger/thirst. She may have eaten the chick's food, however, it was not medicated and was supposed to be OK for adult chickens to eat. Does anyone have any ideas what may have happened to my poor hen?? We did introduce 4 new chicks very slowly to the flock a month ago, the only thing I can think of, is one of them was carrying a disease. If that's the case, are all my adult chickens infected now? What should I do for damage control?