Ok well first off your using miracle grow for nutes? Not the best choice, I find there's really no benefit to
that product where mj is concerned. There's plenty of alternatives just as cheap.
Spraying the leaves with just plain water is ok I guess don't think it does much tho.
Foliar feeding is a dif story... I would get some seaweed extract or molasses even shultz 10/15/10 works
( but there's a million things you could use) well with about 1/3 the recommended dose for watering.
I foliar feed in the morning. If your using mh/hps then you want it off until the leaves dry.
If your using floro, or cfl they can be on for the feeding & leaves won't burn.