first off i dont reccomend using miracle grow it always cause problems BUT since u have already put them in it you have to make sure u never over water ..... when u water them water till the whole top of the soil is moist and then keep watering for a couple seconds so it has time to get down to the roots ull be able to figure it out ... then when u think its time to water them again ... stick your finger or something in the soil about 4 inches down... if the soil is dry that far down then it is time to water again ... also make sure u have your lights 2 to 4 inches away from the lights if u are using cfls ... i dont reccomend using any nutes since u have miracle grow soil it will only kill them