Can someone explain the evolution of Justin Bieber’s voice across these three albums?

I’m curious about the differences in his voice between Believe, Journals, and Purpose. Specifically, what changed in his voice during the transition from Believe to Journals? They sound similar, but there’s something about his voice on Journals that I can’t quite describe—it feels the same as Believe, yet different in some way.

Also, how would you describe his voice on all three albums? On Purpose, his voice has a softer tone, whereas on Believe and Journals, it feels rougher. What exactly makes these changes noticeable, especially the shift from Journals to Purpose?