nutrient burn, ive read some of your other threads, if your gonna start seedlings, dont start them in nutrient'ed soil, SPECIALLY miracle grow, find some unfertilized soil, or if you got limited shops like me, find a spot thats dead, not dead because you knew someone dropped a chemical there, but dead from like, no water, like that spot you get under a car you dont move for a long time because of no water and no sunlight, then bring it in, sterilize it ( throw it in the oven for like a minute at 350 degrees farenheit on a cookie sheet) and then add some perlite bought from a store (walmart carries it) and use that, make a mix of roughly 70% soil 30% perlite