Change it to once a day preferably after the lights come on. What kind of pots are they in or are they in something different? If there is room stick you finger below the surface a little and see if the soil is moist. If it is don't water. Wait till the next day to water. The plants will tell you when they need watering if you wait to water. They will start drooping and such. But cut back to once a day if the soil beneath the surface is dry. Otherwise get a spray bottle and spray the plants and the soil to keep it moist. Spraying help with stem strengthening. If sprayed once or twice hard.

Like I said once a day if the soil beneath the surface is dry otherwise you are over watering. Can water drain out of the bottome of the pots or what ever you have them in?