I shot the exact same broadheads this weekend. I compared the 90grn 4 blade to the 115grn 4 blade. At 30 yds, the broadheds shot an amazing group. Ruining 3 out of 6 brand new 3-49 ACC arrows. Anyway, I noticed that the alignment has to be just about perfect otherwise I can get a slight fishtail. Just in the begining and then it cleans up. If you were to go back further, it would still group given the fact that it has more time to recover. I would check nock alignment and then shoot thru paper as suggested. You may have more than one culprit. But I know these broadheads can fly my groups no kidding were at 30 yds, 6 arrows all touching and sliced carbon off of 3 out of the six. I did this test on purpose and now have to purchase new shafts. I needed to know if I was going to be using the 90's or the 115's this season.

Good luck!