I suggest, if what you see as stalled growth continues for say more than 3-5 more days (or what others suggest), then be concerned. And some "weird" first leaves are fairly normal. I'd presume as long at the visible parts look healthy (as they do currently), you don't have any real problem (other than impatience and worrying too much). Keep in mind, these plants sprouted in cups and were transplanted to your large pots only days ago - give them time to adapt.
If you feel compelled now to look for problems, perhaps calibrate your pH sensor, check your soil (runoff) pH and ppm/EC, etc. Since you aren't all that confident in what you are doing, I suggest check back here if you think you find a problem.