Java fern black spot

Hi all,
        I have been lurking here for around a year, my tank is great IMO,
Thanks everyone!  
        I now have a question that doesn't appear to be well represented in
the archives.  My Java Fern has black spots/blotches and partially
translucent leaves.  A little background, I added the fern, tied to a lava
rock, and in two weeks it was rooted and I removed the rubber band.  Within
another two weeks the fern had grown and started sprouting babies from the
older leaves.  The rhizome had also continued to produce new leaves and sent
out new sections(split?).  A couple weeks after the advantageous babies
appeared the older leaves started getting black spots and some started
turning translucent.  Even parts of the new leaves have translucent
portions.  But some of the older leaves look great. 
        I have a low light, old, 35gal hex, can only get 30 watts of Triton
in it.  Some of the other plants include: Penny wort, two types of Vals,
Ludwigia, Eloda, Apons, Anubus, pygmy chain swards and reg swards, a dense
grass like plant referred to as micro swards, and a couple of Crypts. The
tank has no real algae problem.   GH 180ppm, pH 7.0, temp 77, Amm 0, Nitrite
0, nitrate <70 ppm, no CO2.  I perform weekly 20+% changes at which time I
add 1/4 oz Aquarium Products Flora Boost, 1/2 tsp Kents Plant food, Genesis
and Jungle Insto chlor chlorine remover.  Fish load: 3 dwarf gouramies, 3
angles, 2 cories, 1 Noemacheilus botia, 1 red fin shark, a ram, and 2
pl*co's(bristle nose and common).  
        The penny wort needs to be trimmed every week and the common vals
are 40-45 in long.  I have noticed a slowing of growth in the past three
weeks and have read that Java Ferns can develop black spots due to a
nutrient deficiency, and am wondering if this may be the cause.  Either
Iron, trace elements, or C.  I have also noticed that my pH drops a couple
of tenths in about a week, I know CO2 injection would be a benefit but was
wondering if this is the cause of my problem.
I need to test KH and Iron.  

Thanks for any advise,