In reality, you do not want just a dual-band light for vegetative growth unless you're dealing with very basic plants. Cannabis is more complex so at least tri-band is necessary for decent results. Two for ten plants would be fine. I had a tomato, five peppers, two cannabis mothers, and a strawberry under a single 90w UFO - the tomato and peppers got so large so fast they started crowding out everything else and had to be moved out of the closet and outdoors (needed the hydro bucket for other experiments.)