Most likely just genetics.. My Mephisto was tiny but she isn't anymore in fact her cola is bigger then the other two you looked at .. They eventually catch up.. I grow with led and keep it 24 inches till the stretch is over then I keep it 12 inches..yeah, lets see.. it was a single seed so should have added more variety.. hoping for the best! i was just going through your grow log and your plants at day 5/6 have much rapid growth than my plants.. is it the difference of pot and soil? or the genetics?? what i have read over is that plants in bigger pots start off late due to more space for root building.. your case looks exactly opposite!
btw i chose +speed only because it said quickest time from seed to harvest 7 weeks..