Holes in Leaves

I started using a homemade version of PMDD and need help identifying
what's missing in the tank based on leaf appearance.  Previously, I had
massive amounts of black brush algae which completely blanketed the java
fern and driftwood.  Since introducing drops of Tetra Pond Flora Fin for
nitrogen and potash (N - 0.55%, K20 - 6.60%) green java fern can be seen
reemerging from the black blankets.  A few weeks prior, I began using
PhosGuard on a regular basis to reduce the phosphate from 3.0+ ppm to
0.1ppm.  So the black brush algae is on the decline and a few temporary
varieties of algae are in the tank.  Green hair algae and red hair algae
have developed in spots, but is nothing serious.

What confuses me is the development of small holes in both old and new
leaves (but not during active growth phase).  It starts as a small
colored spot on the leaf, then grows.  Eventually the spot becomes 2 - 4
mm in size and there is a hole in the center.  Small strings of plant
fiber can be seen stretching across the hole.  The largest spot I've
found is 1 cm and the hole is about 5mm.  The spots are occuring mainly
on the various varieties of Amazon swords but mainly on the melon swords
(both large and dwarf var.).

The substrate is peat/clay/vermiculite topped with fine gravel.
Substrate heating with a Sandpoint system.  Florish tablets in the
substrate are about 4 months old (time for new ones).  125g Discus
community tank filtered with 2 - 350 Magnums.

Looking over Neil Frank's nutrient deficiency posting, I see no definite
match to the symptoms.  It isn't snails because the clown loaches keep
the pond snails under control and the spots are appearing on a daily
basis now.  Could it be an overdose of some nutrient?  Is so, what could
it be?  I haven't tested the tank parameters recently, but its been
fairly stable.  ammonium, nitrite and nitrate - 0 (even with the drops),
Fe - 0  (working on finding a source for the PMDD), P04 - 0.1ppm
(YEA!!), GH and KH 30ppm.

Rochelle Williams
williaro at ftmcphsn-emh1_army.mil