Bernard, who, in the first part of the book, fancied himself as completely anti-social, and disgusted with the people and society around him, discoverse that he actually just hated being an outsider, and actually craved the approval of his society and peers. Before meeting John, Bernard sought out solitude, was bitter about life and his society, and wished that things were different. However, after he brings John "the Savage" back with him, he is all of a sudden the popular guy, the guy to be seen with, and experiences a spike of adoration and fame. The novel states,
"Success went fizzily to Bernard's head, and in the process completely reconciled him...to a world which, up till then, he had found very unsatisfactory."
He revels in this acceptance; it reveals that all along, he didn't despise his community, he despised not being accepted by his community, but just passed his ostracized status off as his own personal choice.
Lenina changes in the fact that she discovers what deep, passionate emotion feels like; she experiences the torture of unrequited feelings for someone, to a depth that she had never even been aware of. Before, life was sunshine and lollipops, a lot of warm-fuzzy fun for her. But then she falls for John, and she experiences
"a sense of dreadful emptiness, a breathless apprehension, a nausea"
as she awaits signs from John as to whether he likes her or not. She realizes that she is capable of deepr feelings. She is rejected by him in a sense, and that throws her world upside down for a bit. So the shallow and beautiful Lenina discovers that she can in fact feel at a deep level.
Hermholtz only has confirmed what he has suspected all along, and through John, has the courage to more vocally and actively pursue some of his beliefs and thoughts. With John he is able to take a stand against the society that he has come to question.
I hope that these thoughts helped a bit; good luck!