Some type of Prunus. What part of the world are you in?

Thank u! I’m in Northeast part of the US. New Jersey. Do u think I can save them?

peking lilac tree? I'm probably wrong, but that's what it looks like to me

Thanks Lane. And very helpful Bill. Thank u very much!!!

You're welcome!

After further research, Those are most likely American Persimmon trees (Diospyros virginiana).

Not American Persimmon...even if the leaves matched (they don't), the opposite leaves, bud shape, and bark don't. It does look like a tree Lilac.

I also think tree lilac of some kind.

Melissa, I would track down the name of the landscaping company immediately so that you can find out the identity of the trees as well as ask questions pertaining to their condition.

I absolutely disagree with anyone who says that it's not important to determine the cause of problems as woody plants enter the fall season. This is especially true for aging plants or those that have been recently installed.

What if the issues stem from a pest infestation which can be effectively treated with horticultural oil applications over the winter? Or a fungal/bacterial/viral infection that may require special maintenance tasks?

There is a great deal that we can do in the dormant season to correct, mitigate, or prevent serious pest or disease issues, all without heavy duty chemicals.

That's why Melissa needs to track down the company that put the trees in.

'That's why Melissa needs to track down the company that put the trees in.'

Agree, and their may be a warranty included that would cover failure of the trees in the event something serious would occur so best to keep them in the loop.

Thanks all! My landscaper is MIA though so I need to figure this out on my own.

Probably Syringa pekinensis. Otherwise S. reticulata. Local USDA Cooperative Extension office should be able to identify problem, if you can get representative samples to them during open hours.

Been a bad year here for all my lilacs with all the moisture & humidity we've had. Come to think of it, my Japanese tree lilac has some black blotches on some of the leaves that look a lot like the close up leaf of the OP (pic #3). Our growing season is basically finished so I'm not overly worried about it.

Looks like Syringa reticulata, possibly an Ivory Silk lilac. The lilacs in my fields commonly look like this in the fall and sometimes even defoliate a bit early. And every spring they leaf out absolutely fine. Japanese lilac fall foliage is usually listed as "insignificant." Might depend on where you live but here the leaves just turn ruddy or blotchy and drop.

This is probably relevant. Be sure to scroll down to the last paragraph of discussion, where the diagnosis is given.

https://ask.extension.org/questions/265803

This is probably relevant.

That would explain my problem. Not only have we had one of most humid and rainy Augusts, I been sprinkling the leaves on my Syringa reticulata when I do water it. :-(

Don't know what kind of summer the OP has had but judging from the pictures she posted, it might have been a wet/humid one also.