One of our 16 month old easter egger hens wiped out twice today when she tried running. The first time she actually did a somersault. She's always been one of the more skittish hens, but typically she would tear out of the coop with the rest of them when we open it. I've noticed for the past month, she's more hesitant to emerge and peeks out first. Usually they all run to the front of the house, but the past couple days she has stopped half-way by one of the cars first, and looks like she's psyching herself up for the rest of the way. She's has looked a little unstable, but until today has seemed to run fine. She is foraging and roosting. They are moulting right now so there have hardly been any eggs, so it's difficult to go by that. Her poo was a very small amount, but green with whitish foam. I looked at the poop pictures link and I don't think it's anything other than the small quantity was strange. She did stand off by herself sometimes and was a little slower moving. She also stood on one leg for awhile. I didn't notice any injuries. These hens were vaccinated for Marek's at the hatchery. Any ideas or other things I should check to help identify the problem?