I think same thing buddy intense lights as well as me over watering at a young stage the stem on lower half was little more scraggly than the stem above ground...
I have the lights on half power at the moment and its 30inches away from canopy...
How far did you have the lights for seedlings and what power ?
Slow, incremental increases in light intensity (5% per day) is the way to go with these types of lights in my experience...