These are different issues, neither of which is serious or warrants treatment. The lacy appearance of the brown leaves is called skeletonization, and it is caused by the feeding of chewing insects. (It could be caterpillars, sawflies, or beetles.) They do not cause the tree any harm and late-season leaf loss is not going to affect the long-term health of the tree. Often, by the time evidence of their feeding is this prominent, the culprits are long gone, having finished eating and matured into adults or having been eaten by predators (birds, other insects, etc.).

We can't determine the exact cause of the yellowing pictured, but unless it's widespread in the canopy, it does not appear to be anything significant. Plants under stress from environmental conditions (drought, for instance) can start to shed leaves prematurely, which means they will usually change color earlier than usual as they prepare to go dormant. Sometimes root problems can lead to branch dieback in the canopy, and they can be evaluated by a certified arborist or licensed tree expert (as can any other concerning tree symptoms). Arborists cannot treat or cure every ailment (as some are not treatable, and often there are no DIY options), but they can help to narrow-down a diagnosis as well as look for sources of tree stress that might be able to be alleviated.

Miri