Possible problem

[chewy tabacca]

Blue chromis, with the lights low looks like this, with the lights on he has a nice shimmer. He is starting to look week but is still feeding. My damsel is now singled him out of the shoal and is taking swipes at him.

 

[Diesel]

Your damsel is trying to eliminate him.
Separate the two, if you have a QT put the chromis in there if not use your sump.
If the chromis recovers try to catch the damsel and put him in timeout for a week or 4 while you put the chromis back in to the DT, sometimes this does the trick but do understand that damsels are pretty little devils and the only place for them to be isn't in a glass box.

 

[chewy tabacca]

Ya he usually tries to be a pest, but the chromis (2) usually school with my anthias (5) but this one looks a little on the week side now and the colour is what has me confused, either I never looked at it this closely in the dark or, I thought it might have caught something. The other one is a silver in the dark this one looks like it was dipped in mud

 

[Diesel]

Fast breathing, not eating, hiding, color loss that can be anything.
How long you have the chromisses and when is the last time you had a new addition to the tank?
IMO, he's pretty beat up and primary stressed.

 

[chewy tabacca]

New edition was yesterday, however noticed the chromis before yesterday, breathing is fine, not hiding, and he's eating, Just was worried that the colour could be a disease or something. The discolouration is only at night though which is why ideas confused, I will leave him be for now he still schools during the day

 

[Diesel]

A disease is always possible of course especially if ppl don't do the 8 weeks of quarantine period.
Looking at the eye it looks like it ain't a disease as it is still nice deep black and clear as when it has something the black looks foul and cloudy.
If it is a disease than most likely your other fish have it as well.
Keep a close eye on the chromis but I think the problem here is that little cute DEVIL damsel.

 

[cmcoker]

Looks like stress coloration, I used to see that when they would squabble among themselves. Although Disease can't be ruled out at this point. I would separate the fish and see how he does