Thats alot of plants for a 4x4, probably 1 gallon pots or 1 mega pot. Given these conditions and clean source water, the nutrient solution pH can be anywhere from 5.4 to 6.5 pH, although 5.7-6.1 is preferred. Clones don't get nutes until they reroot. If you don't understand watering yet don't upgrade to irrigation system. Although in 1 gallon pots with coco you will possibly need to water frequently. Jist make sure to do your homework on coco before you begin.
Good luck 👍