Lighting recommendation for and odd tank size

I have a 6.6 gallon bookshelf aquarium that I've setup for my Crowntail Betta. I am currently using a Coralife 24" T5 fixture with a 14 watt single bulb.

Right now I'm growing Bacopa, Marselia Minutia, Micro Sword and Dwarf Sag. The Bacopa seems to taken off and the rest have shown low to moderate growth. The Bacopa has done so well that I'm not seeing any more growth from the other plants now.



So...
Is it a deficiency in lighting?
Is it a deficiency in nitrates or other ferts?

One betta, an Oto, and about five ember tetras are in this tank.
Substrate is 100% Flourite Black, Flourish is dosed weekly, Flourish Excel is dosed every 1-2 days.
Tank dimensions are 24"W X 8.125"D X 9.25"H

Jeesh, you would think that I would've tested for nitrates but I haven't. I think I skipped testing for nitrates because I was using "live" filter media and water from an existing tank to help quick start the cycle.

I did notice the other plants slow their growth when the stem plants started shading out the tank. I wanted this look so the betta would be more comfortable in this tank. Maybe I should pull the bacopa entirely and let the ground cover establish itself.

On a side note, I bought the Marselia Minutia from you, Mgamer, but I've never been able to get it to really grow for me. Any tips?

Old picture, the Bacopa has really grown in since this was taken. Not much has been shaded out but is is noticable.

It might very well be Rotala. I've never gotten a positive ID on that plant before. Some stem plants really look alike to me.