Since only the exterior branches are affected maybe reflected heat off the gravel

and lack of proper deep watering. ...

is there fabric under all that rock ...

as to sun.. which side fo the driveway is this one on.. does the sun reflect off the driveway also?

3 months after planting.. i would tend to figure its all related to the planting.. or aftercare ... and not jump to disease ...

ken

I think am sure it is heat. it is planted close to 2 concrete walls. There is no fabric. yes, I realized it required deep watering, I thought these plants were hardy and required less water and watered very less(I should have known it required lot the first year). I might have left it for a 4 day period, and it turned like this. I hope it revives. They are white marble rocks there, I thought they promote moisture and cold, didn't know those could generate more heat.

The rock mulch shading the soil beneath the mulch and reflecting heat off the top of the mulch are two separate occurrences. Same as with the roof of a building.