Dude take this advice if nothing else, i start all my seeds under leds and i keep them at 20 inches, 160w true draw for veg (you haven’t specified if its 300w from the wall or it is an equivalent to 300w type of deal) and never had any problems. Those lights can’t be that strong imo. Water them when they need it, when the top 2 inches dry. Plants are resilient, after they establish their roots they are not going to die from lack of water easily, but they “drown” very easily in stagnant water lacking O2.