keep it on for the next 24hr of a couple of days, then scale back to an 18/6 timing. I currently have all mine inn a 12/12 like the sunlight, as it rises and falls but that's me, for you 18/6. Keep in mind that timing will shorted over time where it like it. It will show you one way or another, mine always does. Yes, only when top soil dries. If you pick it now, it should weigh heavy, as the soil drys it will get lighter and lighter. I always keep a spray bottle around and spray the plant with good water purified or otherwise, it cool the plant when its in its darkness phase.