i got 24-25oz off two 600W, that's nearly what you got off 4KW! I am a bit confused but the pics look amazing. Maybe some LST next time and keep a twice-daily accurate upkeep of water conditions: ph, ec (and don't forget water temp.:21-22). Hope the younger ones you FIMmed ridiculously early go well: contrary to a lot of info on pages earlier: FIMming is best done after 5-6 nodes and having done this for 30-35 grows with both indica and sativa dominant strains I can confirm this. Also I have done a test comparing FIMming once, twice and three time with the same pheno and twice produced the most (this test was done twice also)...i.e.: 1 main cola to 4/5/6/7/8....then LST and get 7-8 more and FIM all heads...this is the way I do it. And MOST IMPORTANTLY
do not FIM or hst (high stress train) a week before flower because this tends to (for me) start the change while the plant is still recovering and the 'FIMmed' part will not be as well developed.
Hope this helps, good luck and you may get a shock with your next yield if you LST and/or FIM properly....no reason to get less than 100z off 4KW
keep at it!
P