my plants are three weeks old, i grow them under 400w hps. they are in coco. i feed them with advanced hydroponics micro. they growing the 4. leaveset now. the temperature is 78-80 with the lights on 71 when off. the newly growing leaves are fully developed, but they are really thin. why? is this some kind of deficiency? the lights are 30 inch away from the plants, so i think this is not a light or heat issue. its not genetics, cause i growing 3 different strains( ww, bluecheese, blueberry). sorry i dont have any pics, but this guy ( https://www.rollitup.org/marijuana-plant-problems/188365-somethings-wrong-my-plants-could.html ) has the same problem, and my plants new leaves are the same, except they 3 weeks old. wtf is this? help me pls!