Leaf curling down on all sides?

i'd assume it's pretty hot for the younger plants, because it can't have that type of symptoms that early, otherwise.. .so, more likely lockout. Make sure to water with 20% runoff and only after it dries out enough -- top 1" or so. hope they power through it. Next irrigation, you could run a little extra runoff and try to strip it down a tad? diary says pH of 6.5, if that's only what you put in, check soil. (do that first, actually) if pH is off in substrate, have to get that in line first. Seed can power growth for 2 weeks, so very unlikely the severe symptoms you see are deficiencies.