Is this yeast CO2? If yes, then it's highly recommended to use a
compressed
system on tank this size. But with your lighting, you might get away with
a
yeast system.

I'm very happy with my CO2 system. Bare in mind I have 100% diffusion so
none of it gets wasted. It all goes into the water. I've got CO2 coming
out my ears. More than I need.

- (2) PowerCompact 65W 6700K lights.
That's only 1.3 W/g.

Wattage per gallon is an incomplete rating. Meaningless without considering
lamp efficiency. PowerCompacts are T5 technology - extremely bright. You
cannot compare this by a wattage rating in the day of old T12 technology.
Apples and Oranges. T5's are used to light reef tanks. I've got tons of
light, if anything too much.

Have you used Flourish and potassium at the same time?

Yes, for the last several weeks actually.

Have you measured it both in the morning and in the evening?

Yes, the only thing that changes much is pH, and that by only about 0.2.

An iron test is not really a good indicator or iron availability for
plants
for various reasons. Watch the new leaves of your fast-growing plants. If
they are pale or red, add more Flourish.

I've got bright green shoots coming out everywhere. The fern grew 12 inches
in a week.
I always have O2 bubbles on the leaves.

Do the nitrates naturally increase or decrease?

In the old 55G tank the Nitrates usually ran around 30-40PPM. I liked them
in that range. This new tank does not have much nitrate build up yet.

It doesn't seem like you've really tried focusing on plant health/growth
before.

Really. Well I don't seem to have much problem growing plants.
Just can't stop the BBA from growing along with it.

Chris.