osmanthus problem leaf drop
I planted a 1-gal osmanthus fragrans approximately 2 ft in height about 3 months ago on the east side of our home where it gets full sun until about 2 p.m. The soil is sandy to which I added a compost blend. The top of the root ball is perhaps 1 to 1.5 inches above ground with a berm about 10" from the main stem. It is mulched. It did fine until about 4 weeks ago when it began dropping leaves. The leaves develop small irregularly-shaped cinnamon brown areas which progress to covering nearly the entire leaf before they drop. It is not leaf spot as they do not have black and yellow and do not develop holes. There is really no brown or black on the tip either. The bottom branches are dying.
We have had the hottest summer ever with many days in the upper 90s/low 100s. I have been watering it perhaps twice a week deeply (a trickle for several hours). Our home is on a river and we have high humidity. Any suggestions would be greatly appreciated!