I fletched 6 gold tips several weeks ago. Saturday, I fletched 6 more of the same batch. Everything the same, same fletcher, same points, etc. Except the nocks. They fly 3 inches different at 15yds. How could nocks make a difference like this? Just a glance, they look the same. But looking closer, they are slightly different. Has anyone noticed this before? Is there a preferred nock among good archers?