Certified GKH Gardening Expert
Unfortunately, laying anything during the more extreme parts of the year can yield results like this. Watering will be a very delicate balance. You want the roots to remain slightly moist, but do not want them wet. This invites rot and root suffocation.
By autumn, you will likely know what repair needs to be done. Until then, offering proper moisture content, and letting it dry very slightly between watering will be necessary. Adding shade cloths in those spots may help, if you feel that this could be sun related.