Help - brownish plants

[Steve Bansee <stevebansee at shaw_ca>]

Hello all,

I seem to be having a problem with my planted tank.  The problem is as
follows:
Java fern new leaves are not dark green, kinda yellowish at the tips.
Some Echinodorus angustifolius leaves are turning brown and dieing.
Holes in Echinodorus "belyjo" ???
Spiral val leaves are brown.
New Lindernia rotundafolia 'varigated' leaves seem to be growing small.
This tank has been doing great for about two years without any problems
and over the last couple of months these problems started cropping up.
I've been dosing with PMDD and supplement potassium by adding K2SO4,
nitrate by adding KNO3, phosphate by adding KH2PO4, Magnesium by adding
Epson salt, and the trace mix is from Homegrown Hydroponics.  CO2 is
from a pressurized system, lighting is 2-40w compact fluorescent and
4-36" 25w T8 lamps (180watts).  Tank size is about 50 gals (36 long x 20
wide x 18 high). 
I've search the web on nutrient deficiencies and have tried, adding more
Epson salts for magnesium, adding a little more phosphate and nitrate
and more trace but noting seems to help so far.  No visible algae
present in the tank.
The tank don't have that nice healthy green look, it looks dull with the
brown leaves on some of the plant.
I'm stuck right now and don't know what else to try.  If you have any
ideas what might be missing please let me know.

Tank specs.
50 gals
180 watts lighting
pH - 7.0 (Hagen)
KH - 110 mg/L - 6 dH (Hagen)
GH - 200 mg/L - 11 dH (Hagen)
Iron - .1 (Seachem)
Phosphate - >3 (Seachem)
Nitrate - 3 (Seachem)

Steve