With a heavy heart, I'm sad to say that I had to put him down...
Whatever was wrong with him, if it was internal, it started to show when I woke up external. His whole face was white and covered with fuzz, and went straight to his gills and mouth. Poor little guy could barely open his mouth.
I truly did everything I could for him these past few days. And while I'm sad, I'm sure I did the right thing for him. He was so lovely, a bright purple butterfly VT that I found at Petsmart. I only wish that he could still thrive in such beauty.
Many thanks for all your feedback, guys. I'm quite thankful for it.