yours are growing mych faster than my friends nat he is using a 1000watt hps is thaT TOO MUCH LIGHT or is it another factor you think?
im talking about the fimmed spots and new heads
I only give my plants sips of water when they require it.
Flood once a week.
And i use an 80/20 mix of soil to perlite.
This is a lot more work as i have to water them more often but the amount of air in the soil is greatly increased which helps and also these are my own f1 hybrids,from fresh carefully harvested and looked after seed.
True pure f1s as a general rule are 25% better at everything,including the end buds strength.
Good f1s are often cloned continually for their extra potency and vigor and never reseeded by commercial growers.
I also am using blue lights and red lights at all times.
2 cool blue fluro tubes and a dual spec hps,i think it makes a genuine difference and is worth the extra layout to have blue and red spectrums all the way through.
Having a 20% amount of perlite in the soil means that my roots always have air and can never become sodden and heavy soiled.
It also helps to stop soil souring from over watering.
I use filtered water and live in the country so i have very little air pollution in comparison to some areas which also helps.
I have heard the theory that sometimes to many lumens can be damaging to young plants but i dont know to be honest as i have never used any other powerful lights.
Its more likely that he has over watered them and i think this is the main reason for stalling seedlings.
Make them search for water by giving sips on one half of the pot whilst the other side is drier and alternate the sides of the pot you water on.
Flood them only once a week.
All the above is only what i do and i have no evidence of anything