Customer should take a careful look at Tru Green's money back guarantee. Request the money back--try to get it back for the whole year--as if each application contributed to demise of the trees.
Customer may want to threaten to post hundreds of internet complaints about TG online--with nice photos, too. Copies of all written material included.
Customer should have a highly-qualified tree company inspect the problem possibly sending samples of the tree and soil to a lab for analysis.
Also be sure to call you county extension agent for a look see and possibly send to the university extension horticulture lab. IFAS--your tax dollars at work.
There are plenty of young, hungry attorneys in Florida--happy to take 33 percent of a good settlement.
Customer should feel free to call Better Business Bureau, Angie's list, Chamber of Commerce, and the Department of Agriculture--pesticide misapplication inspector. Find out if the guy who applied the herbicides was licensed, working here legally, applied when the temp was too high legally, or wind was too strong legally. Did he read the label? Was he dizzy, light-headed, or affected mentally by the chemicals because he was not given or wearing proper personal safety equipment.
Mighty peculiar that too much rain would fall on one side of the tree and not on the other side.