Hi Dean..

I don't have them planted, but instead I have them
floating in long strands on the surface of my Betta tank.

Okay. Hmm.., what kind of "Elodea" (species) is it..?

They seem to be dying at one end, with the disease or
whatever, slowly working itself to the other
end.

Possibly a lack of nutrients and lightening. Or too high
temperature. Or a mix of all of it..?

Please give us a short survey resp. answers to the following
questions:

How often and how much do you change water..?

How big is this tank? How is it filtered? Do you use air
stones? Is your tap water softer or harder..? How it is
stocked..? Water temperature..?

When did you get the Elodea..? Since when it started to
become "weak"..?

Does anyone have any suggestions on just what I
should do,

Well.., a great chance to familiarize yourself with living
plants..

Did you ever think about distributing them to the brightest
tanks you have..?

because once they are dead, I will no longer
have any live aquatic plants at all,...

Don't worry. You got the Elodea and I'm sure you'll get
other plants, too..! :-)

And neither of the
two local pet stores sell any aquatic plants.

Well.., as far as I remember do some very popular and easy
to manage aquaria plants originally come from the
South-East (USA).

BTW: Google says Miami/Florida has several aquarium
societies:

http://freshaquarium.about.com/libra...s/blclubfl.htm

HTH..
--
cu
Marco