We have buffs. Only about 5. They free range and I have never had any illness problems until a couple days ago. One of my hens suddenly can't walk. She just scoots with one wing down for balance. I've had her in the house for the past 2 nights. She is eating, drinking and pooping ok. I added a little Vit D yesterday to her water and today tried a B Complex in her water. I was reading an article from a 2011 post of a woman with the same problem. Curious as to whether it's just an injury or mareks.