I had a 10 wk old hen that I put down last night. She was not eating well early in the day and was very lethargic. Last night it was very cold and I noticed she was not in the coop. Went outside and there was hardly any life left in her. She was very bloated. I'm concerned about my other birds. Any ideas? They are on medicated feed, have a nice clean coop with plenty of food/water and pine shavings.