The change in attire and the attitude of the characters in the story. In the first portraits they look like beautiful but lost kids. Now they are adventurers, confident in their love, willing to take risks. Kit especially is showing off her ears, whereas it was not even in your description before. The characters are growing in self awareness. They have much to learn still, about themselves and each other, about how to be a couple in a larger group, about how to use their high charisma. Looking the part and playing the part is very much part of who they are. The protrait should reflect that. I wouldn't mind continually changing them.