Why Is My St Augustine Grass Yellow and Spreading

Question

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.

Answer 1

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
https://www.gardeningknowhow.com/lawn-care/lgen/lawn-grass-rust-fungus.htm

Answer 2

Hopefully, this article will help: https://www.gardeningknowhow.com/lawn-care/specific/st-augustine-grass/st-augustine-grass.htm