What's wrong here?

that's a tricky one, I have not seen that type of markings on the leaves before. If we break it down bit by bit we might be able to come up with a solution/plan to help get this on track again. First thing, the leaves curling up is signs of Heat stress. I would try and lower your growing environments temp by 5c if possible get it in the range of 24-27c. Could try and increase the airflow though the tent if its an option. Next up the RH, given that your starting to enter flower you want to get that RH a bit lower. It's not crazy important right now but in two weeks time it will be. Ideal range is around 45% in flower, try to get it down a bit by using dehumidifiers or extra airflow though the tent like above with the heat. thrid point the lights, I've also had some nutrient looking burn like damage on my grow and I thought I was overfeeding them, it turns out the light was to close for the plant. Your light is at 30cm, and you may want to bring that light up a bit. Autos don't like super high intensity unless the other environmentals are locked in. I'd try and move it to aorund 35-45cm, the PPFD map on its product page suggests the min in 12" and the max is 18" but you can go as high as 25" in seedling stage. PPFD is a measurement of how intense the light is, its a lot like PAR maps if you are familiar with them. Net stop is your PH/EC. Any time I see weird unrecognized patterns on leafs it normally has something to do with the root zone in terms of PH/EC or a disease. I do not think your plants are diseased so I will focus on the PH and EC. Have your been monitoring your PH of the water going into the medium or the medium? Its true soil tends to govern itself in terms of PH but that only when its not being bombarded with excess nutrients. I think your PH is out of wack from the amount of nutrients you have been giving them. Next part same subject. your EC, EC stands for Electrical Conductivity, its a measurement of how easy electricity can pass though the solution. It is a stand method of confirm the strength or concentration of your nutrient solution. If this is to high it causes all sorts of issues in the plant. It messes with its homeostasis. This can also be called salt build up. I think because your feeding has been unchecked by a TDS pen, that measure the solutions EC it is crazy high in the soil and causing the majority of these issues. Nutrients are the last part, Your useing BioBizz and that stuff tends to like to be in a solution of PH aorund 6.2. It will also drift down in PH as it sits out. its best to mix the solution up and let it sit out over night for 12hrs then adjust the PH if needed. This will be after balancing out the EC of the solution. PH down can increase the EC as well. But I do not think it will be that big of a problem. In your earlier stages of the grow it looks like you had some issues with overwatering as well. So will want to keep and eye on that. Overwater = droopy leaves with stiff stems attaching them to the stalk. Underwater = droopy leaves and droopy stems attaching them to the stalk. If this was my grow, I would invest in a good PH pen and TDS pen "ec pen", asap. get them today if possible or borrow a buddies. Make a mental note they do require calibration. I would also flush the medium with a lot of water, just water and PH it to 6.2-6.5, this is BioBizz's ph range it likes. If it was hydro, PH would be 5.8 for vegging plants. diffrent PH for different grow styles. Make a note that when flushing soil is it very easy to water log the roots if their is any way to help extract the extra moisture out try it. I hate flushing soil but this one may need it, the feeding ammounts seem crazy high to me, but I could be wrong, this is where the EC will come in handy. I would also move the light up to 45cm and increase the airflow into the tent via the inline extractor fan if you have one. Start their and see how they improve. Best Of Luck and Happy Growing.