Lost my first Discus

[dam-mad]

I have only had Discus for about six months and lost my first one yesterday. Fish was fine when I left for work but by 11 my wife rang to say I had a dead discus :cry: The Dead Discus still had plenty of colour but had a white mucus around it's gill area. All the other discus seem to be fine bar one who has gone very dark and sits alone in a corner of the tank but does come out for food.... Any help is appreciated!

[ILLUSN]

hows your water chemistry? and how big was the fish? sounds like a gill fluke to me try some prazi as per directions on the bottle (1 tablet/20L).