Hi Recticguy! welcome to the frog forum, i wish though it would be under different situation. so sorry for your loss. all you did sounds good, except humidity, that might cause problems. I'm stressing out a word "might", because unless we know different it is all guesses.

have you ever noticed anything sticky around his mouth or nose? have you noticed what exactly was he whipping off his mouth that morning? did he ever looked weird to you, like coughing or sneezing? have you actually saw him eating lately? was he burrowing deep with just eyes sticking out or was just sitting there? have you noticed any change of his behavior comparing to what it was like 3 month ago? you said you noticed him poop - how the poop looked like?