In Chapter 19 how has Pip begun to "break out" and "bloom"?
If Pip has began to "bloom" as your question puts it in Chapter 19, I would humbly suggest that it is rather a barren blooming, as Pip himself is rather perplexed to observe. On the one hand, Pip has every reason to suddenly "bloom." He has found out about his great expectations and is imminently going to be removed from his humble surroundings to the delights and cultural wonder of London, the capital city. He certainly has changed as a result as he contemplates these expectations. However, at the same time, this chapter makes it clear that Pip has not changed for the better now that he has some idea of the future that awaits him. Consider, for example, the way that he reacts to Biddy when she tries to talk to him about pride and how he has changed. Also, note the way that he is unable to sleep well and suffers some strange unease. Note how Pip describes the termination of this conversation with Biddy:
I went out at the garden gate and took a dejected stroll until supper-time; again feeling it very sorrowful and strange that this, the second night of my bright fortunes, should be as lonely and as unsatisfactory as the first.
Contrary to Pip's and our own expectations, Pip is discovering that his great expectations are causing his character to worsen in its essence rather than to bloom as your question suggests. He becomes proud and arrogant and treats his old friends in shameful ways. In this chapter we only observe the negative impact that wealth and status can have on a character.