Hi
@Taunibird , Sue,
that the lilacs have leaf scorch. I come from the land of no lilacs, but hot dry sun. I will throw three things out there. 1-Did you make sure when you put the new lilacs in that they were not root- bound? 2-They need temporary artificial shade, put up a beach umbrella, tie old sheets to poles any thing to give them a break from the sun. 3- Lastly I would water them all continually with slow drip. Let the roots have a steady amount of moisture. When I lived up north our lilacs were on the border of the yard to marsh. At this point I do not think you are over watering. Sue is an expert and if she has any other advice it would be good to follow it. May joy find you this month!