Java Moss and Ambulia questions

I have a bunch of java moss in the front of my 55 gal tank that is sitting on
the bottom on top of the gravel and up against a piece of driftwood. It's
become covered with a lot of long, thin, hair-like growth, some of which is
green and some brown. The stuff is a lot thinner and less branchy than the
original plant, but I'm assuming it's new growth as opposed to algae, because
when I look closely at it I can see it forming some small branch-offs as well
(I'm assuming algae doesn't do this).  
I'm asking because it does not look all that attractive to me, especially
compared to the oringinal plant, and small parts of the new growth are
beggining to show up snagged on other plants in the tank and against the
filter intake screens. Has anyone had something like this happen with java
moss in their tank? If it is in fact new growth, is some of it usually brown?
Will it eventually look like the thicker, more fibrous, dark green original

I also have some ambulia in the tank too. The lighting is approximately 4x40w
daylight tubes and the substrate is a topsoil/vermiculite mix covered by
gravel. CO2 fertilization is by a canister. The ambulia seems to be growing
fairly well, but alot of it, especially the lower-down leaves of the plant,
becomes predominately brown and start to slowly wilt and ,eventually, fall
off (the stems' color seems unaffected). When I cut the plants back, the new
growth shows no sign of this problem (being the attractive light green). This
is true even if the new growth is coming out of a stem with leaves that are
showing brown. It can be growing near the top of the tank, near the bottom,
or a small clipping that I have replanted and there are no problems, as long
as it is new growth. Eventually however, the brown coloration starts
appearing again (except on the the growth up at the surface of the water,
nearest the light. Which is also of course, the newest growth). I've briefly
tried rubbing my fingers on the brownish parts, and nothing seems to come
off, which is not what I would expect if it was something like diatoms. In
any event, I would think the lighting is strong enough so that diatoms would
not be a problem. Could it be some kind of nutrient defficiency? I don't add
anything except dechlor to the water, but I do weekly 33% water changes and
am told that my local tap water is very mineral rich. I have 23 fish in the
tank (mainly tetras and otos), and feed them once a day. This problem doesn't
seem to be affecting any of the other plants in the tank (the brown on the
java moss is not the same kind of thing). Has anyone else had any experience
with this, or any thoughts about it?

                                 Thanks for any help,

                                                Matt MacGregor