It's going to want nutrients soon...but it may be a bit too soon. I would wait until the second set of leaves (its gonna have 3 blades) to grow out a bit more...maybe about 4 - 6 more days, then give them 1/4 teaspoon Grow Big with your water at 6.5 pH. You should of also pick up Fox Farm Big Bloom which can be used every watering and it won't burn your plants. It's a soil conditioner which will give your soil good bacteria. Looking great so far!