Well, there are some good suggestions already. I just want to re-iterate. If you keep the tallest plants along the back and sides, your lights will be able to illuminate the middle, foreground, and sides of the tall ones, giving a better appearance of depth (3D depth) and allowing your shorter plants and the bottoms of tall ones more light.
Embrace your good growth, and let some of that Ludwigia poke out the top (it just loves that). Just let your light get some room to shine.