The spots on your leaves are not nutrient deficiency or burns. I think it's more likely a ph unbalance or over-watering (water your plant every 2-3 days and just around the seedling, not the whole pot for now)
The new light setup seems to be better, but watch it closely the next few days and see if the stem thickens and doesn't grow in height fast :D
Best way to test for burns is to keep your hand there, if it's too hot for you then it's too hot for your plant.
like 1