The problem with Miracle Grow is that it is a general "all purpose", hot nutrient fertilizer. MJ is an unusual plant that tends to be more like Herbs than weeds or general plants. MJ is very need specific, which is why it only grows in certain locations around the planet. That is not to say that you can't have success with MG nutrients, but it leaves way too much room for mistakes like nute burn, toxicity, and too moist soil.
If you have animals, you don't feed them everything from the table to the yard. You feed them specific foods that are best for them to have. You could feed them a little of everything and most will do ok but they will not be able to maintain good health that way. The same is true for MJ.
This thread isn't for the highly experienced and knowledgeable growers to delve into for vast knowledge. While many experienced will look at this to see if there are any good little tidbits of information. This thread is more for the inexperienced growers who want to get around the learning curve and not suffer the same mistakes that the more learned growers have already gained the experience from suffering. The purpose off this thread is so new growers can benefit from our mistakes and not have to go through trial and error to get this knowledge.
Yes you can use Miracle Grow for MJ if you are highly experienced and know how to work the combinations of soil, water, and nutrients to keep the MG from doing more harm than good, but new growers don't need to suffer that kind of headache when there are so many solid nute brands that are specifically formulated for MJ. Yes there are variations of those as well, but that is to allow for the variations of MJ strains and variations of environment.