Chicken with their right leg giving out

[FlappyChick]

Hi, I'm new here and I've been using and learning from this site a lot, since I'm raising my first couple of chickens. So far everything's gone great and I haven't had a problem or my 6 chickens. Recently though, as in today, the smallest, whom we call 'Runt', leg has been giving out. We noticed when we went to check before bed and it'd walk fine then suddenly fall. It'd try to balance its weight with its opposite wing but to no avail. I've looked through some forums and things but I haven't found anything that matches. It's eating normal and acting normal, no signs of pain either. We brought 'em inside so that the other 5 wouldn't peck at him or anything. But, rather than waiting for it to worsen I wanted to see if anyone had any advice on the subject. I'm also looking into the subject of blue cedder tree berries as my mother said she thinks a couple mightve ate some. I'm not sure if it can harm them but I havnt come to a conclusion.

 

[Eggcessive]

Can you post a picture of her standing? How old is she? Could she have suffered a leg injury? There can be some leg bone deformities and tendon problems, such as a slipped tendon that are very common. Was she vaccinated for Mareks disease? I would start feeding her some poultry vitamins in her water daily, in case it could be a vitamin deficiency. SaveAChick, Durvet, and Rooster Booster make good ones for the water. Baby vitamins such as PolyViso without iron 2-3 drops daily can be used instead.