those look like last years flowers ... but that second pic is weird... i cant really tell whats all going one ...

ken

Something is causing the branch tips, not just the blossoms to die since the leaves are in trouble also.

Have you checked the branches to see if there is injury? For instance, holes from some type of borer, or have you had high winds that might have caused injury?

Have you checked to see if any weed and feed was spread on the grass on the neighbor's side of the fence or has someone been spraying herbicide that might have drifted?

yes, there is a possibility our neighbor could have had his lawn sprayed just past the fence you see in the photo. We don't use chemicals in our yard, but this lilac is close to our neighbors house.

I will take a look tomorrow to check for the health of the branches.

thank you!