New guy, Problem with congo puffer!

[Hghlndr85]

Well i will start by saying hi. I am new here and hsve been a memer on mfk for years. I have been in the fish hobby ten years. I love keeping rare,predator fish.
I have a congo puffer that i have had year and a half now. He has slways been active begs for food. He eats pellets,shrimp, shellfish when he wants to. I have found a problem with him recently. He has gone 2-3 week without eating. At first i though he beak may need to be trimmed. It seemed like he wanted to est but couldn't. I sedated him, took and out and checked his chompers. His teeth did not appear to be overgrown.i did trim them while i had him out. He recovered quick but still would not eat. He would circle his food but could not eat it. When i had him out it almost appeared that the skin from his mouth was over growing his beak and was getting in the way of his mouth operating correctm i did notice a while ballon type thing inside his mouth when i had him out. It appeared to inflate and deflate. Any help here would be appriciated i don't want to lose him. Btw temp is 80-81 water parameters are fine.

[Pufferpunk]

Can you get a good photo of his mouth?
What had his diet been like?