+1. Just looking at your light fixture it seems like the type that might have weaker fluorescent grow lights - weaker than the high-end and hotter fluorescent bulbs, that is. If so, you might need to bring the light down quite close to the plants and keep the plants in only 2 rows so they don't get wide of the bulbs.Â
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You can use the back of your hand to feel how close you can get to the bulbs without it feeling too warm and don't move them in super close all at once in case it's too close, but I doubt you want to be more than 6" away from those bulbs and very probably closer, like 4" - perhaps even slightly closer for certain weaker bulb types. It's hard to say without knowing what kind of bulbs those are, how many you have, etc., but even if you are running higher powered florescent bulbs, 6" is likely plenty of distance. Also, as you get the plants closer to the light you may want to think about some air circulation, such as a small fan.
Good luck!