Ok... this is strange!

looks fine to me in terms of health, it's maybe still a little cold outside so it's going slowly. What region are you in?... Maybe try bringing her inside, even if only over night for a couple more weeks. I've noticed that when I start from seed, once the cotyledons pop up the plant spends the next week or so working on its roots. Theres a definite correlation between the roots reaching the bottom of their pot and the top of the plant starting to grow more rapidly. You're in a pretty big starting pot there, so it's probably just reaching down before it reaches up. Be patient, don't over water and you'll be fine. Consider the temps too.