I’m in Central Texas. I'll assume Austin.

Does this look like a fungal issue? No

I have maintained the same fertilization and watering as years past, and it was thick and green before. It looks like you're watering too frequently and not deeply enough. I'm in Bandera and have not received nearly as much rain as y'all have. Still, I have not watered my St Augustine yet this year. In fact tonight I am going to water for the first time this year.

What is your watering schedule (when and for how long do you water)?

When did you start fertilizing, and how often so far this year?

Have you used any other chemicals, herbicides, preemergents? If so, what and when?