Bloated sick golden dojo

[StacyG]

My fish is super swollen all of a sudden, his body looks pale and he's a bit lethargic. I think it's bloat. I've isolated him in a hospital tank, but no one else is sick. The fish store I went to gave me terrible advise and I don't trust him, so I've been looking online for what to do. I gave him water,used conditioner, a bit of aquarium salt and a bit of metalafix, but I don't think that's gonna help him. Any advice would be appreciated. Thank you!