Tang suddenly sick - red blotches

[Gridlock]

Hey everyone. I have a few fish in quarantine, including this Yellow Tang shown below. This evening it suddenly shows red blotches on its skin, and he clearly doesn't feel well.

What could be causing this?

Thanks.

 

[Humblefish]

Bacterial infection: https://www.reef2reef.com/threads/bacterial-infections.191511/

I would treat with Kanaplex + Furan-2 + Metroplex ASAP

 

[Gridlock]

Thanks very much