Nothing drastic that couldn't be chalked up to an artist trying new things but could be seen as another artist commissioned to emulate a style just as well. Differences in shading, line thickness, "brushes" being used (I imagine all this is made digitally so I of course don't mean actual brushes.) I never thought much of it, a lot of games like these can have more than one person on it and depending on the popularity can afford to get some help.
The only real noticable changes are more in regards to the image clarity or "cleanliness" of the images than any changes to aesthetics that would indicate a different artist/artists.
Given that you gave the impression that you'd been following this game's development for some time, you should have been more than aware that there's only one artist. There's literally nothing to say/imply otherwise, and plenty that makes it obvious.
Also, I can't remember the releases for this game being ever more than a month apart, let alone the six that you stated. That includes bugfix versions as well as progress/status updates.
I was giving that other commenter the benefit of the doubt
People saying such obviously stupid things don't deserve that kind of courtesy. At best correction, at worst derision.
Given your own mistakes in replying to him, perhaps try to verify what you're writing before posting it.
