RE: 1/2 shorter arrows shooting high!
If you go to a smaller diameter arrow or different spine arrow you usually need to re tune your bow. For the diameter size difference you would either need to raise your rest or lower your nocking point.
That is quite a difference though. I have never seen a half an inch in arrow length do anything if they are the same arrows. So I would say it's a combination of the extra weight and being nock high on your set up.
Paul