Hi, the yellow material looked like fat in person. It did not appear to be pus. I was surprised to see it and could not tell where it came from. A second chicken died this morning. No apparent signs yesterday except a 1-2 loose droppings. Full body, open mouth heavy breathing this AM. She wouldn't come out from under the perch area. I left the coop to prepare to isolate her. About 1-2 minutes later, I heard a ruckus behind me. When I turned around she was on her back dead. I spoke with my vet, I'm taking the body to the WVDL on Monday for a necropsy.