No specific reason has been given as to why both actors will be departing but executive producer Michael Schur did make a statement: “The news about Rob and Rashida is true — they will be leaving the show after the 13th episode of the upcoming season six. We’ve been working on their storyline (on and off) for four seasons now, and heading into this year, with the two of them contemplating parenthood, it felt like a natural time to move them into the next phase.”
This will be the second time Lowe has left a show during its run, having departed The West Wing during the 4th season. Lowe joined Parks and Recreation at the end of the second season while Jones has been on the show since it began in April 2009. Both Ann and Chris, especially Chris, are great characters and it will be sad to see them go.