Malzahn is notorious for slow starts in September. He is wedded to a 65-35 run/pass game and the Oline is inexperienced and unsettled. Also, no running back has established himself yet.
Of the four players leaving, three were way down on depth chart. The fourth, Nate Craig Meyers was a Rivals 100, 4 star and UA All American. He was unhappy with lack of passes to him. He is a physical specimen with great hands but had trouble separating from initial contact. His brother, a 3rd team linebacker is leaving with him.
There is a lot of unhappiness with Gus and a 7-5 season definitely would put him on the hotseat next year.