I purchased some hatchery stock about two months ago, and got this Jersey Giant pullet in with the bunch. She started not feeling well about 2 nights ago when she couldn't balance herself enough to stay up on the roost so she fell repeatedly. I thought she was just dehydrated but I immediately separated her from the rest of the flock. She continued to get worse. This picture was taken this afternoon, so as you can see her condition has deteriorated rapidly. Can anyone give an explanation? What on earth is this?