Don Heck, of The Avengers, started drawing Thomas’ scripts with issue #38, and he gave them new costumes.
By this time, the book was running on fumes, until issue #42.
Yeah, they killed Professor X.
By this time, the book was experimenting with a new title: “The X-Men Featuring [character name].” This became the new masthead for #44-48. A few examples…
It didn’t make the comic any better. This is a horrid run.