On a cloudy day or in the shade, take a picture of the affected grass from a height of 6 inches.

It's hard to imagine that Texas A&M is on the same planet as the rest of us. I strongly urge you to ignore almost all of what that article talks about. Their discussion of watering is far too complicated, fertilizing is far too intense, mowing height is self-contradictory, and they never tell you what herbicides to use - just what not to use. Here's a summary of what you should be doing

Watering: Deep and infrequent is the mantra for watering. I have an essay on that, but I'll hold off on the deets until you reply with the picture. In your location you may not have had to water yet this year. I've only watered once and, due to these recent, well-timed rains, don't expect to need it again until July.

Mowing: Mow at the mower's highest setting, everywhere.

Fertilizing: Memorial Day, Labor Day, and Thanksgiving. I prefer organic fertilizer.

Weed control: Almost never but if you want to, then use this stuff in mid April and, if necessary, in mid September. Atrazine is the key ingredient.

Insect control: almost never

Disease control: St Augustine responds very well to ordinary corn meal as a fungus control. I suspect that is your problem, but I'll wait for the pictures.

Thanks dchall8 for all the info

Here is the area of concern

Here is the area of good growth which is only 12-18 inches from the other picture.

It does not necessarily look like disease. I had/have spots like that this year, too. I'm not sure why but it's very slow to fill in. We had some really cold nights last winter, so I'm thinking that was it.

How are you watering? Or are you watering? If you are, how often and for how long are you watering? In ground or above ground sprinkler?

Are you more towards Monroe or Shreveport?

I‘m in Northwest LA and water with an above ground sprinkler, 2 times per week for 25 minutes each time at 5:30 AM. So roughly equal amount of water hits both of those areas in the pictures. Soil is clay-heavy, from what others in the neighborhood have told me.

For those ”weak” areas, I was thinking of fertilizing again and then maybe a light top dressing would help. It’s been over 8 weeks since I fertilized. Thoughts?

Good close up photo of affected grass