From what I've researched it looks like over watering to me. If it was under watered wouldn't the leaves be much droopier? Almost touching the stem? Btw Day 14.
Overwatered. A seedling like that, you would have to go 5 or 6 days with no water for it to be under watered. That size, in that pot, more than every 3-4 days is overwatering. Wet