Yup all of them doing it, but I think Marines are especially hard pressed as some parts are not even being made anymore for the non-super Hornets. I remember an article late last year or early this year of them contacting two private museum's looking for a specific part for the nose gear of an F-18. They ended up making them with a 3d printer.
My brother worked with P-3's for the last 14 years before he transferred to another plane and he made the comment to me last year when I visited for Christmas in Hawaii, where he was stationed at, that he once had to go out to the P-3 on display on the base to see if it had a serviceable part on it they needed for an active bird.