Also try:

-Lower your nocking point incrementally and watch for your groups to lift.
-If the shafts you use are spined to be allowed to shot from a broad range of higher draw-weights, incrementally increase your draw weight and watch for groups to start to come center.

If the arrows you use are on the low side of a range of draw-weights that can be used, and your rest, form, and other unknowns are shedding off energy or creating drag, your shafts could be reacting to an "over-spine" symptom regardless what the"charts" say.

I strongly suspect some severe fletch/vane/shaft contact problems.