RE: 7" drop from 10 to 20 yards????
XX75 whats?
If you had said that your POI at 20 yards was simply 7" lower now Vs. the other arrows I would have immediately thought of a lower launch angle created by smaller diameter carbon shafts off the same rest tune..........but you moved your sights to hit dead on at 10 yards and at 20 you're that low? That doesn't make any sense at all unless your lobbing grenades. My bow will shoot almost the same POI at 10yds and 20yds with my 20 yard pin sighted for 20 yards.....maybe a 1/2" high at 10 yards or so.
Did you think to readjust your rest to compensate for a smaller diameter shaft?