My new bow seems to be slowing its shot, even clocked on a speedometer from the bow shop i go to says that with almost every other 1 in 12 shots slows down, but i am not showing any sign of being tired or worn out, the runner of the shop said that my limbs appeared to be in excellent condition, but the 12th arrow always slowed down. should i consider using carbon fiber arrows, or maybe use shorter arrows so there is less weight? Thank you for your reply (if any)