Hi, new to this forum and hoping someone can help!
Two weeks ago I planted a beautiful Kay Parris Magnolia in our front yard. Western facing, full sun, created a garden bed filled with lovely soil with the typical Canberra clay beneath it. It has now turned rather ill looking.

The bottom leaves are becoming dry and crunchy, the flower bud looks like it is drying out (it was a crisp white colour, now a shrivelled brown…) and the plant in general does not look healthy. Getting a brown/black growth from the centre of the leaves. Giving it a water every night (once sun sets) for around two minutes at present.

Planted another one week ago and so far, it looks fairly healthy.
Any help would be appreciated please. Or have I just made an expensive mistake putting a Magnolia in these conditions?
Thanks in advance!!!