I would say raise the lights. I’m not sure if you reported 400Watts as the general advertised wattage on your light or the actual energy draw, but 12 inches seems a bit close. Its a different distributor (Crop King) but if you check out my first generation of grows for reference, including a Hash Plant, I gave them all light damage. Similar situation: everything was perfect but still stunted for no reason. Good luck, I’m sure it will be fine.