I have a 10 year old African Grey. This past year one side of his beak grew into a long V shape point. I took him to a vet and he sedated him with gas and filed it down but he didn't know what caused it. It's been 6 months and I've noticed it's growing again. What could cause this and is there a way to fix it so it doesn't happen again? Is it safe to put birds to sleep with gas?