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Potassium limited?

After doing some research (but unfortunately little testing since I don't have the
test kits), I've come to the conclusion that my tank is potassium limited.

My tank has been set up almost a month now, with 2x55 watts of compact fluorescent
lighting, a laterite substrate, and injected CO2:

hardness (CaCO3):  135 ppm
alkalinity (CaCO3):  101 ppm
pH of 7.1 (7.8 without CO2 injection), which should give me plenty of dissolved CO2

My java ferns haven't done so well; most leaves are brownish. Green hair algae is
present in the tank. My val's growth (the long, slender, fast growing kind -- sorry
I don't have the name) has been slow, whereas it grows a couple of inches a day in
a friend's tank.

The best growing plant has been Bacopa caroliniana, which especially got a jump
start when I added some Jobes fern sticks a few days ago. A little more research
leads me to believe that Jobes sticks won't really help java fern, since their
roots are for anchoring.

I have been adding Seachem Flourish to the water. It has < 0.06 K (sorry no units;
percent?), and I have a moderate number of fish (including two colorful diamond
tetra males), so nitrates should not be a problem. I think that, with my hardness,
calcium and magnesium shouldn't be a problem. Would anyone expect the Flourish to
supply enough potassium by itself?

After reading the Sears et al article, I'm wondering if I'm potassium, and then
nitrate, limited. I have some potassium sulfate and nitrate on order, so I'll be
able to test this out soon enough.

Seeing the green hair algae go away and vibrant plant growth is something I'll be
looking forward to.

-- Stephen

(Sorry for the possible double post; I never did see this go throught the first time.)