Question about adding more like

Hey guy's, right now i have one 400w MH on five plants about 20" away.I was thinking about adding a 125w flourescent to the mix hanging vertical infront of the five.this is the setup.

It never hurts to add more light. I also run a 400W MH for vegetation (8 plants) and for supplemental lighting I hang a set of 75W CFL bulbs at each end of my HID lamp. I like to use a combination of 2700K and 6400K in each set to add a little more red spectrum. That gives me 700W of light and there are no light starved leaves.

The more the better. As long as the heat doesn't become an issue.

More lights for your plants is just always a good idea. I'm about to do the exact same thing.

I think this has pretty much been answered already, but the more light the better, providing heat doesn't become an issue.. But heat isn't the greatest of issues either so, go for it!