The great thing about native plants is that they are tough, resilient and have evolved for eons along with other native flora and fauna to support each other. 
Because of this, some eaten leaf material is expected, and it is actually a good sign of an ecosystem working well. 
We can't tell who the muncher, where leaf parts are actually missing, is, but it looks like the type a caterpillar would do, and they will turn into pollinators like moths and butterflies, which in turn feed others. Some feeding from a native leafminer  is also noted.
We are not sure what is causing the yellowing, though it wouldn't be surprising that heat/drought stress could be indicated given the season we have had.

The best thing you can do for the tree is to keep it watered when we don't get an inch of rain a week (and these guys like moist/wet areas) and keep doing so right up until the time the ground freezes for the winter (which is usually long after leaves of other trees have fallen.)
If it is newly in the ground (less than 24 months) keep monitoring it and watering when needed so that it establishes well.


Christine