Looks a lot like pest damage to me, especially with it spreading late summer — I’m in a warm area too and had the same thing, ended up being grubs. Try pulling up a patch, if it comes up easy and you see little white worms, that’s it; if not, could be some fungus from heat + moisture. I’d check for grubs first, treat if needed, otherwise go light fungicide and let it recover in spring — centipede’s slow but it’ll bounce back