Leaves turning transparent (B.C. Lee's post from May)

[Naomi Mizumoto <naomizu at pacbell_net>]

Hi, all!

I've noticed a new and disturbing occurrence in one of my tanks, and quite 
frankly, it's scaring me. I remembered something similar from a few months 
back being posted, here, and I found it (from B.C. Lee):

http://fins.actwin.com/aquatic-plants/month.200205/msg00675.html

Just in the past few days, I've noticed the rotting of some of the upper 
leaves of my L. cardinalis, in the same manner described by B.C.; I thought 
the cause might be an "algae famine" in this tank and my Amano shrimp 
finally going after my plants. So I moved two of the three shrimp into 
another tank, but today, I was alarmed to see that many more leaves were 
getting transparent. Then I thought that maybe it was the snails - even 
now, they're scraping away at these leaves - but upon closer inspection, I 
see that the rotting appears to be originating from the stem. I'm not sure 
what to make of it. I've never had such a perplexing thing happen to this 
species. It seems to be happening to the tips of my pearlgrass (Amano 
variety), too!

Since June, I've been adding K2SO4 and Flourish Iron. I've been adding KNO3 
since last year with no problems. Also, about a week ago, I ran out of TMG 
and have been dosing with Flourish. I don't think this could cause 
leaf-rotting... In the past two weeks, I've added Hottonia palustris and 
Didiplis diandra. The H. palustris quickly died and was devoured by the 
shrimps and snails, but it was a very healthy cutting from a display tank 
at the LFS. Could the Didiplis diandra have harbored some disease that 
might have spread to the lobelias? I recently heard about a disease that's 
put a temporary stop to aquatic plant shipments from the Far East. Seeing 
as how B.C. is in Singapore and was experiencing this problem with his 
plants, my imagination is running wild... The last thing I'd want to do is 
to draw some far-fetched conclusion. So I'd like to first consider maybe 
K(+) or SO4(2-) overdose or sudden changes in fertilizer. Maybe it's one of 
those things that "just happens" like Crypt melt, when you drastically 
change fertilizer regimen or add new plants... Or look at it the wrong way. 
Up 'til now, I've never had any problems keeping L. cardinalis alive. I 
can't say I've ever been able to get them to look *great* but they've 
certainly never disintegrated on me like this. Other than this, the plants 
are pearling and other than a few green spots on the glass, algae is 
nowhere to be seen...

Anybody want to take a stab at this? B.C., if you're reading this, did you 
finally get this problem under control? If so, how?

-Naomi