Male adult MacMasteri had darked to almost black

[WillmSF]

is this a problem? My male MacMasteri had rreally turned dark almost black in the last 4-6 weeks. Water parameters are good, the female is just fine, he eats like a horse and had grown quite big. His fins are still a nice red but his whole body has gotten a dusky black.
Any ideas?

 

[MacZ]

Would you mind filling out the template for illnesses and post some pictures of the fish and the tank? We got nothing to work with.