Goldfish In Winter

[Groupie]

My pond goldfish have lately be looking sickly where before the colours were bright now they seem to be covered in a greyish slime ,I notice this by looking at them now that the water is crystal clear with the amount of rain.
I have not touched them to see if it is slime or losing colour Any ideas will help thanks.

[jomifl]

If the greyish slime is fungus then they will need treatment ASAP