Rory Donnelly scored for the third successive game as Gillingham registered a 3-1 win over Chesterfield at the Proact Stadium.Gillingham, who had lost their previous two away league games, took the lead in the 26th minute when captain John Egan pounced from close range.But Chesterfield, who have now lost six of their last eight matches in all competitions, levelled nine minutes later as Rai Simons latched on to Sam Morsy's ball to score his first league goal.Donnelly restored Gillingham's lead in the 54th minute as he headed in Jermaine McGlashan's cross for his fifth goal in three games.Harry Lennon made the points safe 18 minutes from time as he diverted in Donnelly's delivery.