Id suggest getting some better nutrients. The issue with your soil is that it may have too much nitrogen not allowing your plant to be flushed properly at the end of the grow. You may not want to up pot, or you could pot up into a lighter soil like fox farms ocean forest or happy frog or roots organic or something like that. Ive used miracle grow soil but only once mixed with ocean forest. Still very great results for vegging plants.
For flowering you want nutrients with more p and k than n. Early flower though your plants will still want plenty of n, more so during the initial stretch. I use tiger bloom once they really get into flowering which is 2-8-4 and supplement here and there with 0-50-30 beastie blooms, and 5-45-19 open sesame depending what theyre asking for. If they get an n deficiency before late flower i switch to 6-4-4 growbig until i feel ive solved the issue.
Its good to have some different ratio nutes around so if you see toxicity of one thing you have the option to exclude it from the feed while still giving the rest of what the plant needs. Sounds like your nutes might work fine so if you want to give them a shot just be very careful not to give too much. I usually go at 1/4 to 1/2 strength of whats recommended and see what the plants say cause the recommendations are always too high ime
Personally would prefer something with more phosphorous than that miracle grow soluble plant food has for veg. With that soil though you probably wont have to worry about any feeding until your in flowering. My 6-4-4 growbig is usually short on phosphorous for my vegging plants in that ratio.