I also just wanted to add, that you might want to try doing the 'harder' questions for practice?
Suppose it's a maths subject. You know that there's going to be at least one question that separates people who've mastered the concept, from people who know it well.
So, get your hands on the trickier practice questions, and do them over and over until you understand them well. These harder questions may be from past exams, or exam writers who publish questions that are reminiscent of VCAA questions. I actually found that certain company exams, like Neap, were more challenging and worthwhile investing time in, when compared to past VCAA exams. Maybe it was because all the questions in these exams were tricky, as opposed to only a few in the VCAA exams being challenging. I also felt that while Neap and TSFX exams went into the 'nitty-gritties' of the course, which the teacher said we didn't really need to know, I still covered those questions. It just made me feel more confident, and helped me to understand the relevant material to a greater depth.
I also think I read that you're doing about 6 hrs of study a day? That's a lot of study time, and I do believe that you are focusing solidly during that time. Maybe just slightly alter what you do in that time, by doing more challenging questions. That should bring you up to the A+ mark.