

Hi garden community. I'm new to gardening and in need of some advice.
I planted 10 x magnolia teddy bear trees 2 weeks ago. 9 look to be doing well but one has wilted terribly.
Soil is sandy Perth soil. I enriched the top soil prior to planting. The plants were watered in well, and planted at correct depth and hole size. I mulched the garden bed after. They are planted along the garden wall which is south facing and receives plenty of light and is protected from damaging winds.
We had a period of heavy rain for approx 3 days not long after planting.
When I received the plant it had a few wilted leaves but I attributed that to damage during transport. Sadly the plant had deteriorated further since then.

I would appreciate any advice on what may be wrong and how to care for the plant to bring it back to health.
Thanks in advance.