Its a pretty big difference for a rather well established style, the author already made haru no noroi and everything stays pretty consistent. One thing I noticed with raise is that occasionally some chapters get incomplete panels or even whole pages, so it could be hiring new hands to lessen the load, but given how different the whole feel is and even the pacing change, I think very likely the author needs a break for whatever reason and a new artist is going over the layout sketches. The art is very clean and nice still so I don’t have any issue with it, I just hope the author is still in good health ;-;
Is the author okay? Seems like a new artist or assistant is helping out, the style changed pretty drastically. But it looks like its following the original artists drafts.