My Discus are getting darker?

Question

I came home the other night (the tank lights were off) and they were all pretty dark, however withing 10 minutes and a lot of water tests (all of which the results were negative) all the colour came back to them. Now I notice on one of them that used to be pale he's getting darker and his stripes are starting to show more. (same with 2 others) There about 6 months old so could this just be them getting there colour or some sort of disease or condition?

More Details:

Number of fish: 6

Tank Mates: None other then a plecto which is a special one who doesn't eat there slime.

Tank Size: 70 gallons

Tank info: One big piece of Malaysian wood, with live plants.

Diet: Tetra-Colour granules, and frozen blood worms (which are guaranteed to be healthy worms)

Answer 1

This is usual behavior for them, once you turn lights on they will change their color to while and than again their bodies will have regular color as always.

if you dont see any white, red spots or cloudy in their eyes, or that they seat and are inactive than there can be a problem

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