Hey, buddy! 👋
This is a phosphorus deficiency, as GaiaGreenGiant says > But! It's caused by a previous nitrogen overdose (bright green leaves with a glossy shine). Right now, you have that shine in the flowering leaves, so you could say that the buds are also experiencing a slight phosphorus deficiency, blocked by excess nitrogen (Gro supplement).
The seed producer indicates a 9-week flowering for the girl to call her ripe! I looked at your diary, and your flowering started in week 5, not week 4 as you noted in the diary! Counting the flowering weeks - there are already 8! So, week 9 of flowering will be week 13 of growth, and it should be the final one (Flush week)! 👌
I wouldn't worry about it at all and would just flush the substrate with water for the next week, expecting further nutrient deficiencies, to consider the harvest healthy! 👌
You're doing great, bro! No need to take any action or worry! Good luck, buddy! ✊😇