Rummy Nose Tetra Lost Its Colour

Hi all,Ive got a shoul of 12 Rummy Nose Tetras in my tank, and about 3 months ago one of them started to lose its colour. Its now almost completly white but still looks well in itself. its eating ok and still swimming about no probs, and still swims with the rest of the shoul. Its head has lost all the redness and the tail has lost the black and white stripes,even the body has lost its silvery look.The only colouring it has is a slight redness around the eye area oh and its eyes have kept there colour. Has anybody ever experianced this before or know what is wrong with this fish. I know that usually when these fish or any fish for that fact loses its colour it indicates a disease or illness but this fish is not showing any signs of either.