Wanted to give an update. I am not sure what caused the drying and curling, but after pruning the dry leaves the plants are actually fine its been about two weeks and they are flourishing. I am assuming it was the water temperature because it affected lower leaves on some plants, middle leaves...
I am growing in an aeroponic system and the plants are about 3 weeks old, I have had no problems until yesterday when some leaves on 4 plants started to curl up and dry. It was pretty immediate, within 3-4 hours. The ph is at 6.1 ppm 990. The plants are about 4 inches tall great growth...