As has always been the case with this show, the performances are fine, it's the writing that is subpar. Adira particularly this year is just filling in the role of young and awkward that was left vacant when Tilly left.
Mary was honestly too old looking to play the wide-eyed newbie by season 2. They cast an actress in her early 30s to play someone who was supposed to be 22, and like a lot of redheaded people, she started visibly aging young.