Jeremy Brockie scored twice for the visitors, putting them ahead four minutes before the break and then doubling the lead after 81 minutes.
Paul Ifill rounded off the scoring with a penalty three minutes from time.
However, they remain third after Perth Glory went down 1-0 to 10-man Western Sydney Wanderers at nib Stadium.
Western Sydney took the lead in the 15th minute when Lacopo La Rocca rose above the pack to head home a cross from the right.
The visitors lost Youssouf Hersi in the 38th minute when referee Kris Griffiths sent him off after he kicked out at Glory left back Scott Jamieson.
However, despite having a one-man advantage for nearly an hour, Perth were unable to break through the stubborn Western Sydney defence in the second half as they piled numbers behind the ball.
The result ends the Glory's three-game home winning streak to start the season and moves the Wanderers into fifth behind Perth on goal difference.