Thrips

Agree that the problem is probably due to thrips. They are the most likely cause of russeting on stone fruits.

"This tree is planted In the grass and gets watered by the sprinklers twice a day. Would this supply it with enough water? "

I assume this is a pop-up irrigation system that comes on for just a few minutes at a time? If so, OK for lawns (although far from ideal) but an extremely poor choice for anything else. No tree needs water daily, even those in very arid climates!! A long and slow deep soaking - as needed; not on any kind of schedule - is what is called for here. Too frequent but inadequate volumes of water do nothing to encourage healthy tree growth, especially of the root system. And an unthrifty tree without a well-developed and established root system is just going to be prone to all manner of disease and insect issues.

You will need to treat for the thrips but they and any other insect and disease problems will be far less of an issue if you adopt proper watering practices!

That is also what damage from Peach Leaf Curl looks like on fruit when it was a bad spring.
Did you have a lot of curl last spring?
Carla in Sac