I purchased 16 Cornish Rock X in September. At 8 weeks they were not quite the size I wanted so I gave them an extra week. I then butchered the largest 5 of them. We let them sit in a cooler overnight and roasted 2 and froze the others. The chicken was awesome and I have never tasted better chicken. I left the the others to grow a little more without the bullies. At 11 weeks we butchered 2 and grilled the chicken in pieces. Did not let them "age". Just killed, butchered, and grilled. It was terrible. Really chewy and tough. Are they too old now or do these birds not grill well or should I have let them age as whole birds. I let two of the breasts sit for a couple of days to cook later and they were also chewy. What is the deal here that these were so much worse than the first birds?