Any lawn repair advice appreciated

Hey lawn legends and grass gurus, I went away for a few weeks and came back to my Buffalo looking patchy. I’m in Western Australia and use bore water twice a week for 15 minutes twice on watering days in the morning and early afternoon. It looked great in peak summer, but recently, it’s started to go brown and patchy. Is it the shade of the above trees? Some kind of desiese? Is it me? (i can change)Any advice would be greatly appreciated as its all new to me.