Check the trunk for little holes and piles of sawdust below them, it could be shothole borers or ambrosia beetles.

Your lawn looks weed free, has there been any "weed and feed" applied? Any other spraying of herbicides lately?

Is the trunk firm in the ground?

No holes and trunk is pretty secure..although I can wiggle it a tiny bit. No herbicides were added to lawn within 20 feet of tree. I did add the 2 items in photos below at the direction of the Home Depot tree expert. The AZ stuff 1X and the Miracle Grow about 1X per week. My husband had set the sprinkler system to 1030 AM...which in AZ is hot enough to burn the leaves! I changed it about a week ago but it is still happening. Could over watering b causing it?

Yes, if water is collecting in the planting hole that is a problem. It is better to water deeply, let the soil drain and begin to dry out and then water deeply again. It could be that the sprinklers are not wetting the soil deep enough but it is more likely water is collecting in the planting hole and doesn't have time to drain before the next watering.

Will do! Thank you from the bottom of my heart for your help and advise! You have no idea how much it is appreciated!