All of the remarks are pretty dead on with problems associated with water absorption and release.
I always will chime in after some one comments about a new commercial site was finished with dying plants within one season after planting.
Did you pull a core sample of at least 12 inches deep and inspect the tilth, color, consistency of the top, critical, subsoils? I do this in multiple areas of new construction sites. Make a map of these zones as you pull cores.
All sites will use this red clay fill to justify low spots and compact the area for foundations, parking lots and side walks. Most times, all the topsoils that is brought in is less than 6 inches for grass to grow on and the plants will suffer even more when the soil is horrible.
I agree that you have poor drainage or not enough water considering this seasons heat and drought. Irrigating a lawn with poor sub soil saturation will only encourage shallow rooting and quick drying of essential feeder root systems.