Bubblegum plants not growing

Hi, I'm growing some White Widow, Ice, Blueberry, and Bubblegum plants. It's been about 6 weeks and every plant is about 8inches high except the 2 bubblegum plants which have only the first set of leaves. Is there something I need to know about these plants that I need to do differently?

They're started from seeds, planted in Jiffy soil-less mix in a plastic cup, under flourescents until 3rd set of leaves. Then moved to 12" pots under a 400w MH light 18/6.

Thanks, Matt.

wow this really is a problem and its very weird. maybe the seeds were rotten? make sure you dont give them nutes until there big plants and water every couple of days with distilled water ( bottled ). buy a ph meter and see the ph of that soil it should be somewere from 6.5-7 no more no less. i dont know what else to say hope they get better