Your plant light from walmart doesn't happen to be one of those blue colored glass incandescent bulbs is it? They are junk. As for the nutes, don't use any for at the very least, 2 weeks. The round leaves(cotelydons) will provide, plus the MG soil has nutes in it. You could probably go even longer before needing to amend with nutes. When you do use nutes, use at 1/4 manufacturers recommended dose, bringing it up slowly over time. Watch how your plants react and if they show signs of nute burn, you know the limit at which the Plant can be fed. Feed only every 3'rd watering.