Plants just hanging on in 10g


I have a 10 gallon in my office, where the plants are just hangin' on.  Tank
specs:  ph 6.8, total hardness ~120ppm, total alkalinity ~20 ppm, temp 78,
1 15watt aqua-glo (minimal, I know but all that will fit in the hood for now),
5ml of Kent's freshwater plant supplement twice a week; fish load 5 gold
tetras, 1 neon, 2 albino cory's, 1 oto.  I would call this a sparsely to
somewhat moderately planted tank, depending on your definition :>) java fern,
hygrophila difformis (sp?), hygrophila angustifolia, and micro sword.  All of
the plants are just kind-of holding their own, and maybe even slowly
diminishing.  I am filtering with an aqua-clear jr., no carbon, no CO2, and
admittedly sparse partial water changes.  Any idea why the plants seem to be
doing so poorly?

Thanks for any and all responses!

David Cooke
david at joshua_medimg.emory.edu
Atlanta, GA