I was mowing my yard saturday and decided to bag the clippings over my leach field since it is really thick there. I would make 1 round and the bagger would be full so I had the kids grab the old lawn tractor with the wagon. FFW to tonight. everywhere I stopped to empty the bags into the wagon the grass has turned brown as in DEAD. Now I have 20 or so perfectly round dead spots in the yard. The puzzling thing is only 2 of the 3 blades did this. I went and looked and there is nothing leaking. Any guesses as to the cause?