Not sure why it seemed to be on, and then moved to shooting broadheads left. A lot of people just starting out move a rest too far to make corrections. When I was tuning broadheads this year, they were shooting about 2" straight high from field points. I know I moved my rest down less than 1/32" to correct the problem. The 400 spine arrows should work fine. IME, it is better to be overspined than under, at least where broadhead accuracy is concerned. I would look at the bow from the back, and look down an arrow shaft that is on the rest and string. When looking down the arrow, the string should appear to be pretty close to the middle of the grip's width. When looking at your bow from the open, or sight window side, the arrow should appear to be level, and cover the rest mounting holes on the riser. If you set the bow up like that, and broadheads are way off, and consistently way off, then go to a good pro shop and have them take a look at the setup.