Than, I was having a similiar experience, skiing very well the beginning of September and last few days off a few buoys. I generally use A2, but my ski partner convinced me to try C2, I was totally amazed at how much better that felt.
In my recent issues I felt like I was constantly not getting across course and turning at the buoy. Since C2 picked me up much earlier and dropped off earlier, I was across course earlier and had time to slow down for the turn.
Tomorrow may be completely different again, but for now, I'll see where this takes me.