I think that foliar feeding at such a young age can do more harm than good. Hold off on foliar feeding for now. (Others opinions may differ)

Check the runoff PH next watering and give a good flush with PH adjusted water.

I use MG soil and generally run into a little N deficiency in the beginning however they seem to pull through it after a week (2 good waterings).

Occasional flushing is good to do anyway.