Thank you for the replies. The temperature in the terrarium is around 80 degrees when the light is on, and the humidity is usually around 70%.

We have quarantined Kermit to a temporary container with new substrate and water. He looks much better right now. Earlier today, his body looked a bit weird - almost an hour-glass shape, with his backend almost as large as his head but the middle still pencil thin - and I was a bit worried that he wasn't digesting the crickets we force-fed him. His shape looks normal now, but still pretty thin. He has spent the last hour with three crickets crawling all around (and even on) him and he doesn't even look at them. I'm going to take them out - we know he ate 2 yesterday and 2 on Wednesday.

I will have to try to find someone to take the frog to for treatment. I really hope that it is an infection that can be treated! I've been reading about some scary stuff (red leg, metabolic bone disease, etc.) and it all sounds bad. My son will be heart-broken if we can't get it figured out!

Thanks again.