Sick Mozambique help needed

My adult male mozambique is showing signs of sickness, but I have no idea
what's wrong.
His fins are clamped and a little ragged. He's been hanging about the
surface lately and not eating. His balance is affected as he doesn't seem
to swim "upwright". His missus knows something is wrong as she stays close
to him offering moral support.

Another interesting point about the pair, is a couple of months ago their
already large lips seemed to get a bit bigger, and the colouration of the
lips changed from grey to a white patch in the middle of the mouth! Not
sure if that's related - I put it down to getting older - something I can
relate to!

The tank is a non-aggressive mixed cichlid lot with no other fish showing
any signs of sickness. The mozambique is the largest fish in the tank.
http://www.dvs.ca/fish for a look at the tank. Water conditions are good.

Any ideas or things to try to help this guy? I don't have another tank
available for isolation, btw.
Thanks for any suggestions,
Rob