My plains garter recently has this sort reddish colouring along the right side of his head close to his mouth and now had reached his mouth, only at once side I'll get a picture but he's a little un cooperative when it comes to his head.

He is eating fine active but does tend to lie with his body upwards a bit more than he used to.

I'm thinking of taking him to the vet as I had a boa with an respiratory infection years ago and I'm concerned he may have the same.