Questionnnn

i’m on season 8 when Jax and Brittany, Stassi and Beau, and Kristen have left. why did they leave and i saw a picture of Brittany’s (terrible sorry girl) reunion dress and it looks a lot more recent. so she comes back??? and what is the valley is that what jax and brittany went too?
would ask google but last time i looked something up a few seasons ago it spoiled a divorce among wit some other stuff so……