Why Was Dr Andrews Fired?

Aaron Glassman steps down due to his poor health. He is later fired for firing Doctor Jackson Han against the wishes of the board to save Shaun Murphy's job. However, he is rehired as a new surgical attending by Dr. Audrey Lim.

How did Dr Marcus get fired?

Unlike Marcus, Jackson didn't have the patience to deal with Shaun and decided to fire him. Marcus trieds to convince him to change his mind but Han was having none of it, so in a surprise move, Marcus fired him during a board meeting.

Did Dr Andrews get divorced?

At the end of season 4, it's revealed that she has decided to move out and end their marriage and has already begun a relationship with someone else for unspecified reasons.