I'm hoping this is vitamin B deficiency and not mareks! This rooster and a hen was laying around, and then stumbling around. I isolated them, The hen died but the rooster is staying the same. Hatched May 18th they are coming up on 12 weeks old. I'm giving them probiotics on their food, which is fermented scratch grains and layer pellets. And vitamins in their water ( crushed 5 B complex tabs and put them in my 5 gal waterer) and nuti drench. Started giving the rest of the flock the same. Before it was just the food and the water. I was gonna upload a video but cant figure it out. My birds are rotational grazed, we use a premier one poly fence and move them to new grass every third day. Fresh water and fed daily. The bird in question is the biggest bird in the flock, hes really tall. And wont come up off his knees, is having a hard time with balance, and toes are curled up. He seems to be making it to the feed and water. Heres some screen shots of him trying to walk. Hes trying to stay up right by putting out his wings.