mcscurver

need help for dying plants

help!!!!!,my babys are dying.tested soil,nitrogen was depleted.added nitrogen.ph level at 7,plants are in a4 by 4 grow tent kept at 75 degrees at 65 percent humidity.600 watt led grow light is about 24 inches plants on a 18 hour on cycle.have power ventilation and small fan inside.water plants every other day.do the need to be transplanted into larger containers?Please help,I do not know howto save them