Red sores, loss of appetite, odd swimming behaviors; it definitely sounds like a bacterial infection (which is why the anti-fungal treatment wasn't helping). Please do take pictures and answer Michael's questions, because poor water quality is a likely cause for bacterial infections. Also, you said you have fish, but is Claude your only ACF? Do you have a spare tank to place him in? It would be easier to clean and medicate if he was in his own hospital tank.

I would suggest treating the bacterial infection with Maracyn II or Maracyn Plus. Do you have those two medications in your LFS? And if you don't, thankfully they're both on Amazon! Remember, if your filter contains any carbon, to remove it before you start the medication.

I'm so sorry Claude isn't feeling well (by the way, I love the name Claude!), and I hope he gets better soon.