Okay, this is what I decided:

I'm going to keep all inhabitants, including the pleco...
I'm not going to add a 5th glowlight tetra.
I have fertilized the plants with the API root tabs, and replaced my bulb (because it was 2 yrs old).
I am going to see how it goes for now, and not soften my water.

I also added 3 peacock ferns (thought they were pretty).

I tested my water at the lfs and my nitrates were at 40 ppm, 0 ammonia, 0 nitrite, and pH came in a 7.8.

I'll post pics of the progress with the plants

AND- Thank you so much for all the info Carlos and Bill! You guys rock!