Hi, 

The shedding could be from squirrel damage or possibly one of the twig-boring beetles; neither is a concern for the trees overall health though.

We can't see enough detail in the leaf spots as the file size won't let us zoom in on the photo, but they might be a gall, as there are many that are common in Oak trees ( one of these). Also these are not a concern since they don't harm the tree. Mature trees can easily deal with leaf shed and new leaves will come out. 

Supplementing some water in the root zone of these mature trees wouldn't be a bad thing in the high heat. Especially since we have had different degrees of drought like conditions through the state this year. https://extension.umd.edu/resource/watering-trees-and-shrubs

If you are concerned for the overall health of your trees, given their size we would recommend consulting with a certified arborist to give you any recommendations or in person advice on maintaining the longevity of these trees. 

Emily

Hi Emily,

Thank you so much for your help! I do have higher-res pictures but I didn't attach them to the prior email since I didn't want the message to get too big. From the images you linked, it looks like the leaves have jumping or sequin galls, and we do have squirrels in the trees so that may be what's knocking the leaf clusters off. Some pieces of larger branches have come off as well, but they look like old wood, so I figured that was normal; I've attached a picture of one as well.