It’s hard to say. 

Photo 1 looks like the area around the lilac and other spots have turned yellow which makes me ask if there was an herbicide used near them.

Photo 2 s- the same. Were these plants getting plenty of water? I know we have had a wet spring but when they are young they need consistent water. 

Photo 3 this looks like lack of water or a root borer. I see that it is planted with rocks as mulch. Is there plastic under the rocks? That would limit the water that is getting to the root of the hydrangea.

Hi ,Do you think my lilacs could have Verticillium wilt?My lilacs seem to wilt overnight.

I heard this yers people asking about a lilac issues.

This year people are asking about issues with lilacs.

This year people are asking about issues with lilacs.

Yes, we have had a number of questions about lilacs this year. Many of them are exhibiting leaves that dry up and turn brown quickly. 

There are a couple of culprits that could be at play here. Many lilacs in my neighborhood are Turing brown and drying up. Our very wet spring followed by dry heat has contributed to this. It will not kill your lilacs.

The best thing you can do is to practice good clean-up. Clean up all debris and put in your municipal leaf collection. Do not compost these at home. 

http://plantclinic.cornell.edu/factsheets/lilacbacterialblight.pdf

https://extension.oregonstate.edu/news/how-recognize-treat-avoid-lilac-bacterial-blight#:~:text=Sources%20of%20the%20disease&text=Wind%2C%20rain%2C%20insects%2C%20tools,rapidly%2C%20especially%20during%20rainy%20periods.