You are not giving it enough Gro - that would cause many issues. I would give equal portions of all and make sure your ppm does not go over 900. Otherwise dilute with RO water.
Also I wouldn’t jump into defoliation - the plant in flower light mode will start stretching fast and it needs all the leaves that stored nitrogen it can get
Definitely not mildew. The somewhat uniform spots indicate missing nutrients - possibly not the NPK but rather micro nutes like trace minerals. Have you been adding those? Eg chromium or manganese?
Looks like heat stress - check the leaves for meaty feel - they might be too brittle and dry. Also 68% humidity is way too high, 50 is better. You use laser termometer to check top leaves temps
Definitely over fed and potentially having heat stress. Flush with RO water or spring water from crystal geiser or equivalent for few days. Some leaves will improve and many will remain ugly. But at least your buds will continue to grow well. (Any dry leafs - prune those off)
Check the PH as the water drains — likely it will move down. Simply flush the plant with higher PH water like 7 with nothing in it until your measured drained water is about 7 (I recommend to do that after you transplant to a large pot with perlite as others recommended)
It’s possible that the soil makes the water too acidic. I would recommend immediate transplanting to coco coir to a larger pot. Water flush with PH of 7 then let it dry a bit a watch the growth. Your leaf structure indicates that plant is not observing nutes.
Turn the leaves upside down and check for spider mites. They appear as dark specs. Use your smartphone video recording with magnification to see them move around.