lighting question

I am growing 2 Aurora Indicas under a 400w setup. They have been in veg for 28 days and are about 12 in. Growing in 15 gallon containers w/ Fox Farm Ocean forrest souil and FF nutes. I have had them under MH and was wondering if I put them under HPS if they would get taller? would it effect the stretch during flowering? I run 18/6 right now. So should I switch to HPS for the last couple weeks of veg or stay w/ MH. thx in advance for your help.

if you're using fifteen gallon containers, you'll prob need more than 400 watts to flower two plants. thinking like 600-1000 watts per plant if you veg them enough to take advantage of that much soil...

and if you're using ocean forest, don't bother with too many added nutes until you hit heavy flowering, IMO

I plan on moving up to 6oow my next grow, so should I switch to hps now for a little strectching?

600 for both? or 600 a piece? 15 gallon pots, right? if you have two 600 watters for flower, let your plants get big. if you only have one 600 watt for flower, you probably wanna spread out your canopy as flat as possible to fill a whole 3x3 space with canopy. if you let them get too big you will be outside of this space in 15 gallon containers. either these plants are gonna be BIG or you may be using too much soil for what you have the light to accomplish.

doing the math in my head, we put 6 5 gallon pots under one 600 watt, so this would be the same amount of soil as 2 15 gallon containers... however, i feel it may be more difficult to manage a canopy with plants this big. the light intensity of one 400 or 600 watt light is not enough to penetrate very far into the canopy. plants in 15 gallon containers will want to be very bushy, you will need to spread this bush flat with lst or screening, supercropping, topping, bending and pinching. anything below the first two or three tiers of buds are going to get exponentially more scraggly. with our 6 plants in 5 gallon pots, they don't thicken up as much as giant trees and we can spread more into a workable canopy. not that what you have can't be done with a single 600 watt light, it is just a little more difficult. don't over-veg.

ok, so for this grow under a 400w lamp I am supercropping, they are both very bushy and about 12 in. So should I go ahead and flower now?

we used to flower 4 foot tall plants under a 400 and be fine. looking back on your posts your growing indica, so if they don't stretch you may be able to get them a little bigger. just account for them doubling in size during flower. if you tie them over now you may not need to screen to get plentiful bud sites. just remember that a 400 watt light only ideally covers a 2x2 area, and try to keep your canopy in this area to maximize your yield.