He was a juvenile about an inch long when I found him, so I don't think he's dying of old age. He can't be older than 7 and is most likely only 6.
he was kept with one of my other frogs for about a month this spring when my youngest frog (the one who wasn't eating and pacing back and forth at the front the terrarium, who is now my most voracious eater and has grown significantly) wasn't eating and couldn't have the competition from the other frog. But I already had that one for about a year and he's definitely never shown any signs of illness, unless it's just something his young, vigorous immune system can handle that my older frog can't.