Light colored spot on Kole tang

[meermann]

Hi guys, sorry I wasn't be able to take a photo with better quality, it constantly swims around LRs.
But: my Kole tang has a light colored spot on his side. It's the same coloration like other skin, but significantly lighter.
Bought him yesterday evening.
He eats with greediness brine shrimps/flakes/slim algae etc. and doesn't itch himself. Looks like the spot isn't bothering him at the moment.
What's the disease and should I cure him and how?
Unfortunately I have no quarantine tank, fish population is: 1 Chelmon rostratus and 1 Clownfish (and this Kole tang).

 

[meermann]

Took a picture with my old DSLR, the lens is too slow so... quality is not perfect as I did it in manual mode.
But also he has a small white spot on his cheek.

 

[meermann]

Quick update: the pale spot is still there, see the pic.
But also I found a few of dark spots on another side :(
Is it dangerous?

 

[meermann]

And look at this side when I bought it in my LFS: completely clean. Now there are a few dark spots :(

 

[ReneMiami]

Hi guys, sorry I wasn't be able to take a photo with better quality, it constantly swims around LRs.
But: my Kole tang has a light colored spot on his side. It's the same coloration like other skin, but significantly lighter.
Bought him yesterday evening.
He eats with greediness brine shrimps/flakes/slim algae etc. and doesn't itch himself. Looks like the spot isn't bothering him at the moment.
What's the disease and should I cure him and how?
Unfortunately I have no quarantine tank, fish population is: 1 Chelmon rostratus and 1 Clownfish (and this Kole tang).

It could be flukes. Give it a fresh water dip for 5 minutes. See if white seeds like things fall from the fish after around three minutes. If that is the case treat him with PraziPro.

 

[meermann]

It could be flukes. Give it a fresh water dip for 5 minutes. See if white seeds like things fall from the fish after around three minutes. If that is the case treat him with PraziPro.

My Copperband Butterfly that died before had the same stuff in FW dip. White flakes or seeds or whatever. Anyway, did FW dip previously and also 1 day dip with Tetra Medica TremaCestoNemaEx (Diflubenzuron), because of Praziquantel is prohibited in Germany

Now I see the fish swims in the flow of powerheads, possible Velvet Fish disease :(