If anything is going on health wise, I seriously doubt it isn't reversible/treatable. He will be fine.
Corns are easy peasy compared to BP's (very adaptable and flexible and not nearly as sensitive or picky); it sounds like you have some mitigating circumstances here, even if it is just the stunted growth.
He will be fine. Don't beat yourself up. Instead, put that energy towards figuring out what is going on and CONTINUING to do what's right for Corny.
You are doing great, just keep it up.
My pleasure, RE replying. I, and others on the forum, are here for you. Just keep us posted and we will happily help in any way we can!
David
P.S. Corns are poop machines and drop some hellacious butt bombs! A sample will not be hard to get, agreed!