I have lost a few young chickens to some kind of sickness. They each died a few weeks to a month or more apart from each other. Then today one of my adult Americana's died. She was acting absolutely normal all day, eating, drinking. When I went out to lock them in for the night she was laying in the yard. I picked her up and she was very weak and floppy. She then had what looked like a seizure and died shortly after. It all came on so quick. When I was holding her I noticed how skinny she felt along her breast. Back to the younger birds they pretty much did the same thing but not as floppy acting. They didn't seizure at all. Does anyone have any idea what this could be?