I have two customers that have 10 by 10 areas of grass that are thin but tolerable in the spring, but then they almost completely die out come mid summer. Both spots are around 10-15 ft. from trees, they have exact similar symptoms. I did a solid test on one of the sites, and the PH came back low, but I don't think that is the problem. Does anyone have similar problems? Can someone lend a helpful thought? Thank you.