Adastra thinks it was the beginning of popeye, so it was probably a bacterial infection. Since he had it when I brought him home I don't know for sure. It's still kind of there, but not NEARLY as much as it was before. For now I'm just treating with warm, clean water but if it sticks around or gets worse over the next week I'll start the salt treatment. He's a spunky little guy, and he doesn't even seem like he notices that anything is wrong, so I'm not all that worried.