Discolouration on a perc

[ed99]

Folks,

I have a mated pair of true percs. Recently I noticed some discolouration on the female that I don't think was there before. It seems that the colour loss is underneath the scales as opposed to be a growth on top or in the skin. The male does not have this and they both eat as heartily as they always have so I don't suspect a parasite or disease right noe. Any ideas what it is? Here are a couple of pictures:





Thanks,

Ed