Arrow spine refer to the stiffness of the arrow and its ability to flex when launched off the string (dynamic spine). Your arrows are too weak. The arrow is flexing too much once it is leaving the string which is causing erratic arrow flight. I would not even bother to try and tune with a weak arrow because from shot to shot you are going to have a lot of variance.

You will see your groups tighten up when you match the correct arrow to your setup. Refer to Easton's arrow selection guide for help with this. As you move up in draw weight/length, you need a stiffer arrow so the arrow does not deflect too much when it leaves the string.