I have a playpen full of show line Barred Rock chicks. 16 of them, about 4 weeks old, with a couple that are a week or so older. Noticeably a bit bigger. They've been fine and dandy all this time, but yesterday I came home to one of the biggest pullets dead on the floor. Can they really be trampled to death at this age? I've never lost one this old. Anything that would just randomly kill a seemingly healthy chick? They're all vaccinated for Marek's, so it couldn't be that. On medicated feed the whole time, so shouldn't be Cocci either. I'm a little stumped, beyond just a fluke internal malformation of some sort.