Care for Anubias nana

I have good plant growth in my 75-gallon aquarium (I sell my cuttings back
to the fish store, usually make between $15 to $60 a month, depending on
which plants need pruning).  However, my Anubias nana's aren't doing well.
The older leaves tend to develop yellow spots and holes.  Is this normal for
Anubias nana?  Am I supposed to keep pinching and throwing away older
leaves, or are there something wrong?  They flower regularly though (there
are usually one or two flowers at all times).

Tank condition:  pH 7.2 to 7.4 (with yeast CO2), 120-W fluorescent (VitaLite
and Ultra Tri Lux) on about 11 hours a day, fertilize with Flourish and
occasionally with Tetra Flora Pride, nitrate under 10 ppm.

Thanks for any idea,