I saw acorns in the first picture and then what appears to be sand or agri. lime on other areas. What is that white stuff???
Looks like slime from total over watering!! I know the Melich 3 soil tests will not tell you of impending disease unless you acknowledge to the State that you want a toxicology report. This will probably cost you and the customer needs to know up front. Find out how much first. Under those trees will have grub issues, possible armyworm issues....and I noticed a pine tree.......sap problems because of insect attacks.
It is hard to tell from pics and more in depth studies needs to be done first. I mean, disease or fungus has to be detected with microscopes and involved tests.
What grass type is this??