Some people start on nutes early. I personally don't suggest it, but to each thier own. Big Bloom however, I don't use it, so correct me if I'm wrong. I would think this to be a nutrient additive for the flower phase, as suggested by the name of the product Big "Bloom". That sounds like a waste of money, IMO...
Anyways, sorry Bagger...
Once your plant has sprouted, it should be under light. 24/7
Generally you want to plant your seed, or sprouted seed, and water well. Then leave it be. As the soil dries, it will promote root growth as they grow and stretch to find moisture. Just water them every 3 - 4 or so days, just depending on your conditions and how quickly your soil dries out.