Can’t figure this one out

Looks like an early nutrient deficiency (some growth is very pale, others dark green) though there may be more going on. Your soil looks decent so its kind of early to hit a nute deficiency unless you are causing it or your ph is off, which can also cause it. Since fixing a ph problem can fix a nute problem, while adding nutes won't be absorbed if your ph is off, the first step is usually to check the ph: in soil, 6.5 is ideal but anywhere between 6.3-6.8 will work. Outside that range and some nutes won't be absorbed and can be locked out. You could also have a nutrient toxicity: have you fed it recently? The leaf edges look a little battered which could be from chronic wind burn (I did this my first grow) or that plus a deficiency (which I did several of my first time). On the nutrient toxicity side, Cal-Mag might do that though you'd have to give it a lot I think (in soil you don't need much). On the deficiency side, it could be magnesium (possible if ph is off or even if it isn't if you aren't providing it by now somehow). If your ph is off, correct that and see what happens: it should stop the discoloration, and if it doesn't (or your ph is fine) you may need to add some Cal Mag. That'simplest for a deficiency in either or in iron (since it has that too). If you can't get that right away, epsom salts are among the possible alternate sources I think (you'd need to google that to verify and for dosing instructions). Deficiencies in calcium or magnesium can also cause that upward curl. Though so can light/heat stress or over-feeding or over-watering. Those are the main suspects.