If you start your seedlings in miracle grow soil it will burn your plants. It is too nutrient rich for seedlings. I always germinate my seeds first, and then after they sprout, I plant them in seed starter soil. When my plants are in the vegetative stage of growth, I transplant them into a 1 gallon pot with some good quality organic potting soil. Don't start feeding your plants until the third or fourth week of veg., unless the leaves start yellowing before then. A lot of people like to sart their fertilizer solution at 1/4 strength, and then increase to full strength from there.