My St. Augustine lawn in Jacksonville, FL is developing some patches. Some are very slow growing patches that are going bare. There's one patch in which the grass is very green, but is duller in appearance from the rest of the yard. I think my auto irrigation system is doing a decent job of watering the whole yard. I don't think its a lack of water. My neighbor says he's noticed it in other yards and his too. He thinks its a fungus for which you can get granules to broadcast. Thoughts, anyone?