Miracle Grow is not a professional medium, however, cannabis is a weed. Higher quality soil brands would be better, but that doesn't mean you cannot get fantastic results with MG! I always recommend newbs go for a soil that is "set it and forget it" for their first few rounds. Soil like Fox Farms Ocean Forest provide all the nutrient required for 1-2 months, and gives you lots of time to figure things out.
It doesn't matter the medium though, it cannot be too wet or too dry. Despite popular belief, wet/dry cycles are not good for plants, they are very stressful. It is best to keep your plant consistently moist, you do not want it to be excessively heavy with water. pH for store bought soil is the same as HYDROPONICS! Store bought soil has no dirt in it! I shit you not, read the bags, no dirt. This means they are AMENDED SOILESS POTTING MIXES, NOT SOIL AS ADVERTISED. pH 5.5-6.3 and keep it steady. 5.9 is what most of us like to use, but that will vary if your soil pH is high or low. You can also adjust your soils pH with dolomite lime before you plant into it.
Omit nutrient from your feedings, just water only. If it doesn't look like it's turning round, give it food. YOU HAVE TO MEASURE HOW MUCH YOU FEED THEM, FULL STRENGTH WILL ALWAYS ALWAYS ALWAYS BE TOO MUCH! 1/4 STRENGTH ONLY FOR SEEDLINGS BETWEEN 2-4 WEEKS.
Dude, absolutey rake the surface of the soil with your fingers, it's very good for plants! It will definitely help, be careful not to catch any surface roots. You said that's generic soil right? You might want to look into exactly what you used and what is in it. If it's really really cheap stuff, it is possible that it has actual dirt in it.