Web Master:
Hi Ellis
The plant in the photo appears to be Casuarina glauca 'Kattang Karpet'. This cultivar is susceptible to fungal infections, Powdery Mildew being the most common especially during the cool months if the plant is getting insufficient sun.
Fungal infections can be treated with an organic products like Eco-fungicide and Neem Oil or non organic chemical like Mancozeb.
General maintenance - regular watering to keep soil moist through the growing months, avoid watering during the winter months. Fertilise in spring and early autumn, a native sustained release fertiliser will ensure the plant gets a steady stream of nutrients.