Miracle-Gro soil is OK, IF you don't add any nitrogen nutes (you should NOT add any nutes the first two weeks of any seedling, anyway) ... the nitrogen is pre-added, to take you all the way to the flowering stage ... (MG soil works, but other choices tend to be better) ... yellowing leaves early in growth is due to either a nitrogen deficiency (not in your case), or over-watering ... over-watering is probably your culprit ... :smokin: