The people that flower at 3 weeks have likely started cuttings in an aero-chamber of some sort, and are planting roughly 12 days after being cut. The plants are 3-8" tall, and the roots are 2-5" long.

You have to be patient. Growing from seed takes time to get going. As long as they are still alive, don't get too much or little water, and the roots don't touch any ferts yet, things should be fine. Just keep the light back from them a little for a few more days, and keep them warm. The warmer it is the faster they will grow, but then there's more chance of mold or rot. Just watch carefully for that if you turn up the temps.