Well, Nino's not wanting to moving on and wanting to be their clone selves forever because she was scared of being left alone was one.
As a parallel, now we have Miku's not being able to consider herself a quintuplet, and think the other quints are different in a better way if compared to her, is the other.
I'm half sure Ichika's was that she saw how Itsuki was devastated by the less of their mom, she forced herself to be the mature one, while never wanting to do so.
Itsuki's was hinted that it was because of Rena's death and she trying to cope with it.
We never had anything about why Yotsuba decided to change (first) or help everyone, though