a change in artsyle over time with a single artist is pretty natural so in most cases so long as you and your readers can recognize the characters it's usually fine.
Personally both my artstyle has changed as well as the designs of a few of my characters but they're still for the most part recognizable (or at least i hope they are
)
Another instance that comes to mind is Josh Tierney's comics Warm Blood and Spera where he does the writing and chapters of the story are drawn by several different artists each with their own unique styles but you can still identify and recognize the characters.
I think it's something lots of artists have probably gone through at one point or another where the style changed or the design wound up a little altered but so long as people can tell who it is or what's happening being 100% on model shouldn't be too much of a concern. Heck even major franchises mix up the styles and designs used for their characters so I don't think it's so so bad