I was so happy when all 13 of my first batch of chicks survived to go outside to their run. However, a week or two later, when one of my rooster was 6-7 weeks old I noticed that he was hopping on one leg on morning. Other than that he seemed fine, just wouldn't put weight on one leg. The next day was the same. He was eating and drinking fine, just not using one leg. The third day however he was week and would not stand at all. I separated him from the rest of the flock and he continuted to loose strength and died a few days later. Any ideas why what seemed like a simple injury went downhill so quickly or what the cause may have been?