If his arrows were shooting fine before he pumped up the draw weight, and are shooting bad now, there is an obvious solution. Go back to the poundage he was shooting before.

That' s about all the advice anyone can really give you because you didn' t give enough information. What brand, size and length arrows is he shooting, what kind of fletching, what weight points, what bow it is -including model, cam, draw length- whether he shoots fingers or release, what rest is on the bow... That' s the basic stuff we' d need to even try to give specific advice.

Best guess according to what you told us, like C903 says, is his arrows are underspined for the extra draw weight.