Did you do anything that migh have caused this, like a recent feeding? I have seen severa; pposts over time that mention similar issues appearing suddenly about 2 weeks into flowering. I think it was determined to be a nutrient issue, probably an imbalance. When leaves "taco" upwards, it is usually heat related. Taco-ing downward is somewhat new to me except in cases of possible nutrient burn and insect damage, such as spider mites, which I didn't see signs of.