Java fern prob

Season's Greetings all.
        I'm having a problem with some Java fern in one of my tanks.
I've been growing this plant for some time in various setups with
consistently good results.  However the java fern in this tank, secured
to a piece of driftwood is beginning to turn brown.  It seems to start at
the base of the leaf and work it's way up.  I had this problem in one
tank, snipped of the offenders and no more problems.  However, in this
tank it seems to be a bit more persistant.  This tank has been setup
about a year with several other species which are doing ok. (vallisneria,
Bacopa carolina, H. Polysperma, Sagittaria natans, Anubias nana and
salvinia. Tank parameters are normal with some nitrate, 7.5ph, moderately
hard water, duplarit balls in the substrate and Flora Pride added as
needed.  I'm thinking either alleopathy from some competeing plant or
maybe a disease specific to Java Fern.  Any ideas would be appreciated.

				Ho. Ho.

					Miles Morrissey
					mmorriss at sophia_smith.edu