I used my 400mh last round of veg. I saw significant growth but I topped late. Vegged for 6 weeks 6 of them. 4 got up to 36" or so. Lol. Happened quick too. Blinked my eyes and they exploded. I'm now using 4ft t5 4 bulbs. Due to heat in my room. I have a 1000w hps enclosed exhaust hood. 400mh...