Update:
The meds you recommended should show up soon, however, I wanted to share where we're at in case this helps in the future. I believe I have an outbreak of blue-green algae (cyanobacteria) in one of my tanks (I can smell it), so I treated my two main tanks with Blue Green Slime - Ultralife Stain Remover. When looking at the Silver Dollar Fish last night, I kept counting them as I couldn't find the infected one; eventually realized it's healed up very nicely. I'm not sure what that means as far as what the fish was suffering from, but it appears to be doing great now. I'll just keep these meds in my hip pocket for if this problem returns. Thank you again for the help!