Stars $5.5 vs $6.5

[Xanthro]

I've been examining my results in Poker Tracker, and in the in Stars $5.5 my ROI just under 30%, but in the $6.5 it's (35%).

The hands don't seem to be that different, but obviously the with the fast raising blinds, I'm doing something fundamentally wrong.

Oddly, I rarely play a hand in the $5.5 until the blinds hit 150, so you'd think I'd play better with faster raising blinds.

Any hints on what I may be doing wrong in the $6.5 so I know where to research better?