Stay away from Nitrogen in the late spring and summer months and supplement with Iron. The Iron will cause the green you are looking for and not create the added stress of growth during the hot summer months. Also, you are definitely watering entirely too much. Your lawn will thrive on an inch of water a week. That is a deep watering all at one time. If you need to figure how long it takes get a coffee can and mark it at 1" and put in the path of your sprinkler. Once it fills to the 1" mark you know how long it needs to run in each zone.
P.S. I believe plants thrive on CO2 as opposed to O2.