hi! I take Biology, Chem and Maths, all for AQA (can’t help you with psych, sorry!) For Biology, Mrs Estruch on YouTube is fantastic. Physics and Maths Tutor have hundreds of questions for all subjects - this is important in making sure you get good grades as you can not rely on just memorising content. I would also say to get the Biology with Olivia Notes - they follow the spec and are really good to learn from. The notes are also answers to common exam questions, which is vital for AQA especially as AQA Biology mark schemes tend to be very specific.
Although I do not do OCR chemistry, chemrevise is a great website which has notes for every chem topic. I believe they have notes for the different exam boards, so do check them out. Memorising these notes would bump your grade up for sure. They also have a practical guide. I would also recommend chemguide - another good website which breaks everything down for you. Again, use PMT for exam questions to practice. On YouTube, Allery Chemistry and Elliot Rintoul are amazing channels to learn from.