Mexican Lime Tree Problem

[kingpickle]

I bought a new house in a Phoenix suburb and had the back yard professionally landscaped two months ago, including three trees: Arizona Yellow Bell, Pomegranate, and Mexican Lime. All three were doing well until a couple of days ago. Almost overnight, the Lime tree leaves started drooping and falling off and the tree looks like it's dying (other two tree doing fine). My landscaper is stumped. Any ideas?

[Sylvain]

What temperature do you have? And where is the tree? Is the ground wet?