Chris, yeah the Heritage 90's are the same thing as mine (.530 spine), just with the wood grain finish, although mine are 8.6 gpi.
I took off the 6 strand string and went back to my 10 strand and it settled everything right back down.
When I first got this bow I was driving tacks with it. I later made the 6 strand string and my groups have not been what they should be, even though my bare shaft shoots good. I guess the skinny string was just putting too much horsepower into my shafts.....
I have 5 dozen arrows all the same, so I really don't want to buy new arrows just to get a couple more fps out of this bow.
She's back to shootin' like an ACS now!!