Responses
I think it's more on the artstyle as a whole changing to have bigger features, and emphasize less os smaller details (it happens with most long serializations), but also Ludwig *was* older in that first chapter, so I think that's why the hairstyle isn't a complete match; from the flashbacks too you can see his hair length fluctuates a bit (which is nice to see they actually pay attention to that)
I re-read the first chapters again and although the current art looks good, I still find how the artist drew Ludwig better in the first half. He looked more mature? Taller and broader too. I also like bob type of hair too. Ahh but oh well, he's still cute