These are diagrams of the grow. They show growth relative to light placement. In the first one, you can see that the HPS isn't perfectly centered and the plants on the left are growing taller and wider. The second diagram shows the relative heights of plants after the MH hood was added. Note the lateral placement of the lights, I tried to depict the scale as accurately as possible. Adding the 400w MH turned the "runts" into dominant-in-comparison plants within 2-3 days.

Obviously the lights aren't ideally placed, but I just wanted to point out how the plants reacted in this particular situation.

As soon as I can move the lights to a better positioning (a few inches to the left, I think) I'll make a new scaled diagram.

FWIW, the light spectrum emitted by a a MH and an HPS working together looks awesome.