Your groups were all 3-4" what? Left, right, up or down in relation to your expandable heads? Hard to help you without more info.

But in general (for right-handed shooters), if your broadheads fly a few inches left of your fieldpoints, you can cure this by moving your rest in VERY slightly (like 1/32 of an inch at a time). Yes this will make your fieldpoints hit to the right as well, but the POI of your broadheads will shift more than the fieldpoints, and they will eventually merge to one POI. Apply the same logic to cases where you broadheads hit high, low, or right of your fieldpoints. Move the rest toward where the fieldpoints are hitting.