sounds like has stuck food/substrate in his mouth, like Bogertophis said you or a herp vet might want to check his mouth for anything out of the ordinary.

I switched to newspaper that way i can spot mites if there ever had to be any , its perfect for my humidity conditions where i live as our humidity is almost 80% year round , easy to completely clean right away and best of all no dust and no swallowed substrate.

Keep an eye for open mouth like symptoms and any swelling as well.

Best of luck!