I think you're right. He's beginning to show other discoloring. I know that I've been overfeeding as I was going on advice from my local store (which was 100% wrong!). They know a lot about fish but not much about frogs as it turns out.
In any event, tank is not stable and I know I need to completely change the water (in the process of doing that). I'll look into those treatments because I'd hate to lose the frog if there's something I can do. I've been looking online and salt treatment sounds like an option; just need to figure out how to do that!!
Very grateful for your response. Thank you.