It's hard to guess what "errors" may have led to that grouping without actually seeing you shoot. It could be a number of things, but I'll narrow it down to the top three likely candidates.
Different arrow mass. Lighter arrows drop less. I don't know if you've ever weighed your shafts but it looks like a matched set, so I'm guessing this isn't your culprit.
Depending on your cant, changing nock point on the string can cause some serious movement. Just 1/32" up or down can make the arrow move inches by the time it gets to the target.
This one is the most likely in my opinion, anchor point on your face. Same as with the nock point on the string, tiny movements in your anchor point will raise or lower point of impact dramatically. I recently suggested to my wife that she raise her anchor point because her groups were awesome but consistently 6" high at 15 yds. She went from her cheek bone to the corner of her eye and it did the trick.
You can play around with all these variables and see how they effect your shooting. Hopefully you can get it tuned in, but hey, all your arrows are in the target so you past the hard part.
