nutrient deficiencies

I have a bit of a problem that I would like to see thrown into the ring 
and see what the debate turns up. I have an Amazon sword plant ( I 
apologise that I do not know exactly what species, it is the type with 
permanent juvenile leaves) that has a problem. At first I thaught this 
was confined to this plant and then I noticed that a couple of the 
ludwidgia leaves were doing the same thing.

The leaves become kinked at about half full length and both the leaf and 
central vein are both tightly bent at this point. The closest thing that 
I have seen that looks like it is a mutation in maize called "knotted". 
The difference is, unlike knotted, it does not cover the whole leaf.

A virus seems unlikely in the absence of necrosis and that the ludwidgia 
also has the same problem. The leaves stay green and give off oxygen at a 
great rate. It seems likely that I have a nutrient deficiency, but what? 
The symptoms are unlike any terrestrial plant symptoms that I am used to.

What have I started doing about it? Well I have incresed the water 
changes, cheked all the water perameters that I have kits for and started 
adding extra potassium. 

Ok to the tank
1" of red iron containing soil
1/2" of peat
3" of river gravel (about 5-8mm)

Fish: 2 2" Boesmani, 1 2" lucustrus, 1 2" trifasciata (coen river), 2 2" 
taterndina ocelicauda, 2 2" flying foxes and an ancistris catfish. A bit 
heavy, but at the moment I do not have a choice.

Plants: variegated hygro (4 bunches), ludwidgia, rotala sp 3 bunches, 
ambulia 2 bunches, bolbitus sp, java fern, thai fern (probably a java 
form), various crypts pontederifolia, wendtii, becketii, lutea etc, a 
marble queen sword and a juvenile ottelia alismoides.

Co2 via yeast, 70W of NEC HG flourescents for 12 hours a day with no 
sunlight, pH 6.8-7, kH of 70ppm. gH of 120ppm. Nitrate and phosphate I 
have no clue about, though at a guess with the fish load it would be on 
the high side. Filtration is by a simple pump with a fine filter on it, 
no external canister etc. This turns the water over about 5 times an hour 
with little surface agitation. Iron is kept at about .2ppm.

Any help with this would be greatly appreciated.

Peter Hughes