Sick pleco. What's going on?

[Bristlenose 94]

So, I've had an L350 (Peckoltia pankimpuju) for a couple months. He arrived a really great specimen. Beautiful, full odontodes, very active and hungry. His odontodes shed when I got him, but soon after they seemed to start growing back and his tail streamers had some new growth. Now, for the last 3 days, he's been breathing rapidly, his streamers are melting at the tips, and he won't eat. He's even swimming to the surface to gulp some air on occasion.
What happened? Every other fish in the tank, including an L056 and a Hypostomus luteus, are all doing just fine.

He is in a QT tank now, with both an HOB and sponge filter to really oxygenate the water, and just got a dose of API general cure.

Anyone got any advice?

[bekateen]

Now, for the last 3 days, he's been breathing rapidly, his streamers are melting at the tips, and he won't eat. He's even swimming to the surface to gulp some air on occasion.
What happened?

Honestly, this sounds like ammonia burn to me. I appreciate that you say all other fish seem fine, but the finnage loss and surfacing to breathe seems like classic high ammonia, perhaps coupled with low oxygen. Your therapy of qt with general cure sounds okay. Maybe add another air stone and keep water immaculate.

Good luck,
Eric