Heat stress would be my first thought as well.
If not heat stress, I'd immediately suggest mg def...leaf twist can be indicative and it's not ALWAYS associated with Ca def, which shows with the characteristic rust spots. My Strawberry Cough's showed Mg def. early, added some epsoms, the leaf twist went away. I'd be suspicious of pH problems though in your case since you're in soil...I'm in coco with exact pH in and out with every feeding, so my problems are def related...you might have a somewhat low pH causing lockout. What are you feeding and what's the runoff coming out at?