I have several pittosporum hedges and recently had 18 planted along a side fence. All but five of them survived to get to a reasonable height. Now one of these is also dying and one of my established plants from my front garden has died. Can you give me a reason as to why this is happening? I am sending a photo of the one that is currently dying. It's leaves are beginning to shrivel
From this image, the entire shrub looks wilting and may be in need of water.
Pull back the mulch.
Check the soil moisture levels. Soil should be slightly moist. Long and slow watering followed by a slight drying of soil is the best.
But avoid overwatering, roots in wet, soggy soil will rot.