Thread Fin Butterflyfish looks greyish

[dishum]

Hi Guys, one of my Thread Fin Butterflyfish has come with some disease in the past 24 hours. The body has gone greyish and it isn't swimming normally. Can anyone make a diagnosis please?

 

[Humblefish]

Is it the entire body or just patches of grey? Either way, that usually denotes a bacterial infection. I can't tell for sure from the pic. Is this a new fish?

 

[4FordFamily]

People also have different observations - velvet can make the entire fish appear "grayish" (lighter and slightly powdered) across the whole body a day or two before it succombs to the disease.

Hard to tell from the photo. Are there any other symptoms? Is it swimming in to power heads? Scratching? Acting cryptic and hiding? Eating well?