Some fish do change colour as they get older, especially commons, shubunkins and comets. This is most likely just a natural thing. I have found with my fish that there colours are brighter and better if they get enough light. I have noticed this more with my tuxedo platy, if she doesn't get enough light she goes more brown than black and if she gets enough she goes back to black, so I am pretty sure it isn't the light affecting her colouring unless it has increase the speed of her colour change.

When I moved my orandas into the 40 liter (right before they got to move to the current tank), Berry lost most of the color on her wen and also turned a paler red allover, I was worried she'd turn completely white! Once I moved her to the current tank with better lighting she started getting the reds back again and they even spread a little (could be thanks to the better water quality).
It could be just the way the light shines on the fish and also loss of some pigment, but it might not be as bad as it looks. Have you looked for some bulbs that enhance reds in fish? If they eat lots of vegetables it might also contribute to loss of reds, krill, carrots and color enhancing pellets will help with that

Sounds great
I bought krill from ebay, here: (Link is not visible to guests. Please register to view.)
But they should be available as frozen or freeze-dried in most pet shops as well. I have a gel brine shrimp mix that contains some krill too.

They are really big though, so you'll need to break them into smaller pieces and soak them before feeding them to the fish unless they're about 4 inches long at least

Nossie do you think krill would be good for flash and Merle?

Ok thanks I will look for some!