Why Is My St Augustine Grass Yellow and Spreading
It started in a couple of areas and now it's spreading in other areas. I've put over and out on for grubs and other pests, put weed and feed out in late March.
Certified GKH Gardening Expert
If not insect pests, it could be a fungus of some sort. Treating the area with a suitable fungicide for lawns may help. Here are some possibilities as to what types, though there are many and it's difficult to say with any certainty which one. https://www.gardeningknowhow.com/lawn-care/lgen/grass-fungus.htm
Hopefully, this article will help: https://www.gardeningknowhow.com/lawn-care/specific/st-augustine-grass/st-augustine-grass.htm