what he means is that most people consider miracle grow to be an all purpose fertilizer,rather than strictly MJ fert,like advanced nutrients,so with the miracle grow you will have some deficiencies.......me i grow in hydro but to tell you the truth if i were to use miracle grow,i would just use less of it....just to be on the safe side,but the bottom line is that i would still use it
and to avoid over watering,let the soil get dry,if youre growing in pots(you are)let them get very dry...you can tell by how light the pot gets,then water down the stalk of the plant...about 4 ounces directly down the stalk,weed likes to be thirsty a lil bit