Orange shoulder tang black patchy spots

[cashmilladakilla]

Hello everyone, my orange shoulder tang over the last few weeks has gotten these black patchy spots on him, they started off subtle but over the last few days they have went nuts, he is also flashing (he has his entire time i’ve had him, 2+ years) I am setting up a quarantine tank this weekend and i’m going to take him out and get him some medicine. Does anyone know what’s wrong and what medicine or antibiotics would be best for him? (sorry the pictures kinda suck I am not at home right now and it was very hard for the person to get proper pictures of him)
The clearer picture of him is from a few weeks ago, it’s the one I took, but now as you can kinda see in the more blurry one he has more dark patches and is very pale skinned. Thanks for any help