I've been mowing a lawn for about five weeks now. Last week he called and said he had a large brown spot. I checked it out and it did, it was down hill from his pool that he also opened that week, concluded he washed some stuff off there. Anyway the yard is developing brown spots here and there he thinks I'm mowing to low (3 inches). I mow all me yards there and I don't have any problems there. A little note: This is the first in five years that he didn't have chem lawn treat his grass, could this have anything to do with it? Is too early for grubs right?