You may have over-watered! Is someone else watering behind you when you don't know it? Are you using a sprinkler system? Sometimes my sprinkler system comes on when I don't know it! Like when someone else thinks the yard needs it and it doesn't. I had a similar problem and it was fixed by backing off of the fertilizer and watching the water. Try it for a week and see if things don't turn around. Also try a product called "Soil Soup". I just love the stuff. It's a combination of Compost Tea, Horticultural Molasses and Earthworm Castings with aeration. Bubbles in it that is...Great stuff. Good luck!