Hello Danny
Looks like Dollar Spot!
This occurs mid-spring to early autumn, an extended period of leaf wetness will encourage this disease. Most likely when nitrogen fertility is low and growth is poor.
The main symptoms are numerous small (no more than 50mm) bleached spots which may coalesce to form larger, irregular patches. Infected leaves appear water-soaked at first then bleached. Leaf lesions have a characteristically bleached white centre with a reddish-brown border. White 'cotton wool' mycelium may be noted in early morning. Recovery is usually rapid, as roots are not affected.
Note: This disease is more common in the North Island.
Maintaining adequate fertility is often the easiest method of preventing attacks of dollar spot. Fungicides will give good control of dollar spot, ask your local nurseryman for an available product.