Thank you, Josh! All of the water parameters are perfect—temp is 76 degrees and all API water test results came out great, and he is the only one acting weird or sick. He came with a group of sickly Cory cats, sadly. The others developed a fungus, he has the odd symptoms noted. I have 2 adult Cory cats in my main tank doing well. I also went to a different lfs and got 3 more...all of which are doing well. Just this poor guy.