Alright fella, you've got the gap thing fine.
Also, what the other geezer was trying to say was..
Move your light as close as you can without burning the plants, to tell if its gonna burn them, put your hand a certain distance from the bulb and see how close you can get it without your hand getting hot, that'll give you the best growth
Light intensity deminishes with distance, so for instance using a HPS during the seedling stage would be awful because the plants would have to be so far away from the bulb that the overall running cost of the bulb would not weight out the benefits from it.
Defiantly look into getting some nice small say... 20w (100w equivilent) 6500K bulbs, or they might be labled as (cool white) or summin like that
They'll help bush those babies up, plus yu can place them from around 1 inch to 5 inches away from the plant, check mine journal to see what they're capable of
Also mate, i'd look into vegging for a bit longer, basically the longer you veg the bigger a plant your gonna get, that why mother plants are used for ages to produce clones, and then once they veg out a bit after taking no clones, they grow HUGE.
Usually a good length of time is a month in vegging, however i hate to be the bringer of bad news but i think they'll need a bit longer
But patience will be the ultimate test during this grow, so if you dont have it, start getting it!
Also, do you have any spare clayton pebbles left mate? If so, place them over the top of the rockwool cubes and generally to near the top of the pot, this way more of your stem is gonna be burried, thus making it stronger due to the length being shortened
Instead of pebbles you could put a bit more rockwool around the top, doing the same thing
Right, im gonna stop talking before i go on too much
P.s. : One thing i just remembered, how deep have you placed the rockwool cubes within the netted pots? I used to do DWC and i placed the rockwool cubes with the seedlings in WAY too high, like... nearer the top of the pots then the bottom, it took ages for the roots to finally show through. If you move them down a bit they'll get more water, if you move them up a bit they'll get less, work out whats best for you, because if they're soaking it might be worth moving them up slightly, however if they have roots just ditch that idea!
Hope this all helps buddy and anything else you need just ask
i'll try my best to answer when your next online