Brooooo WHAT DID I TELL YALL!!!! These Perms and combs man. Legit I had the same thing happen to me where I averaged around that 95-100% mark previously but I got absolutely abused by those god damn perms and combs qns and there was an assignment the term before that (where I and several other students got mislead by a teacher who didn't mark the assigment) so my average for the yr now is a 91.4%
(IN A MFING RURAL SCHOOL SO THAT MAKES IT 1000x worse). Back to ur qn tho, tips I'd prolly give you is remember to treat qns in exams like you would in the ucat and section out easy marks and the ones that will take a longer time to calculate. Another thing is, from what I can see from your post, it seems that you have become crazy stressed over yr 11 marks, indicating that you may suffer from lots of anxiety whilst you do your exams, which often leads to you focusing more on the consequences of not doing well rather than actually fully trying to prevent that by applying what you know into the paper. Meditation will most likely help. Always note that there's heaps of time to improve, and prelims are coming up, which is likely your best chance to move up in rank if you rlly even care that much (given yr 11 doesnt count towards anyhting).