Rasbora In Trouble

[Mariposa]

Hi one of my harlequin rasboras disappeared for about a day and now has coe out of hiding but his colour is faded and he looks like he has a dusting of what powder all over his body.
It doesn't look like ich but something isn't right.
Anyone know what this is?
Please help

 

[The-Wolf]

does the dusting look like gold dust?
if so it could be velvet disease (Oödinium)

The best treatment that I know of for velvet is any copper based med.
due to the toxic nature of copper, it is advisable to follow the makers instructions to the letter.