Rule of thumb--
always water ALL the soil until saturated and a small amount leaks out the bottom of the planter-- do this just as the lights come on or if outdoors- early in the day..
DO NOT WATER AGAIN until the top 2 imnches of soil are dry and the planter feels light- but before the plant shows signs of wilting..EVEN IF they start to wilt- after watering they will bounce right back- as long as they didn't completely wilt.
Many growers ruin their plants by watering too little at a time or too often... if the water doesn't saturate the soil, the roots stay up toward the top of the planter-- shallow/smaller roots = smaller weaker plants... and over-watered plants are prone to root rot and other diseases-- and they can 'drown" if their planters drain holes aren't big enough for sufficient drainage!!