How far should my light be?

How far should my light be from the top of the canopy? There’s an 8 inch difference from the tallest plants in the shortest one. From the tallest plant it’s 44 inches to the light. From the shortest plant it’s 52 inches to the light.

A hell of a lot closer than that.

Buy an IR thermometer gun and move the light down until the leaves are 27-28c.