Bhs eye problem

[Westley Price]

Difficult to tell exactly what is going on the the picture, but what often happens is that a mouth issue results in swelling around the eye, which makes the eye look recessed with a bit of pink skin showing around the eye, especially on the lower side.

Maybe listen for wheezing when he breathes and open his mouth to check for anything abnormal. That could indicate a mouth problem.

[immaculate geckos]

Another cause is a mite bit him next to the eye and a small infection has built up either way there is swelling around the eye with a good possibility of an infection of some kind.
A trip to the vet would be my bet and keep the new snake away from your others.