Great looking sod! How's the soil underneath?

Where do you live?

How long do you water? Once a week is too frequent this time of year...for USA.

How high/low do you mow? It looks a little short. It should be mowed at the mower's highest setting once a week to once every 2 weeks. If your lawn care company insists on mowing at any other height besides the highest setting, find a new lawn care company. St Aug thrives at every height except low. I've grown it up to 32 inches tall and it looked amazing.

To make sure the pictures are understood. The 1st three are to show the progress of it being established when it was re-sodded.

The bottom 2 pics are of it now. As you can see it's not as green or thick as the 3rd photo.

I live in Florida. I try and water only once a week early in the morning (more if it's really hot out or the blades fold in half). In the summer I was cutting it at my mowers highest setting, near 4" from concrete to blades. Recently I went down to about 3.5".

Compared to some of my neighbors yards and even my side yard the front is not nearly as thick. The sun hits the front of the house in the morning and the back at night. The only trees I have are in the front. I thought chinch bugs. But since it's being treated every 2 months and the signs of circular damage patterns are not present it must be something else.

I can take more photos or create a diagram to show shade, sidewalk, driveway relationship etc.

It's fungus.
Set the mower back up to 4". There's no reason to lower it for St Aug .

How long do you water it?

Will raise the mower height up from 3.5" to 4"
I can check my lawn pest control notes to see what fungicide they used last month (which clearly has not been working). I did mention corn meal to him and he has never heard of it. :(
I used the tuna can tricks to get the proper 0.75" - 1" per watering. I water once heavily to get that amount and it takes ~70 mins for the front (the area of concern).
What makes me lean towards it not being a water issue is I water in the early morning and not at night like my neighbors and they water once a week for 40mins or so. They too have trees in their yards and do not spend nearly as much time on their grass as I do, so either I am overthinking it or I need to get soil samples and take it to the next step.
Thanks dchall_san_antonio(8 San Antonio) for the help, I see that you spend alot of time on the boards helping others. :)

Zman has a similar issue to his yard. Linking that thread for future readers and discussion. https://www.houzz.com/discussions/thinning-st-augustine-yard-dsvw-vd~3466529

I just realized you said, 'pest control' every 2 months. I've never
applied a pest control product, and you do it every 2 weeks? In all the
years on this forum I don't think I've ever seen anyone with a regular
insecticide program. I would stop that, get the watering frequency
right, and see if the lawn improves. In addition I would get something
organic on it soon. Repeated applications of insecticide will kill out
the population of beneficial insects. The microbes are important to
keep happy in the soil. The general classifications of microbes are
bacteria, fungi, microarthropods (i.e. insects), and protozoa. These
microbes are so intertwined in the food chain that the scientists refer
to it as the soil foodweb. When you remove an entire class of critters
from the food web by using insecticide, then the important roles played
by that class do not get done, or they do not get done
efficiently/effectively. By stopping the application of insecticide
(and I'm talking about COMPLETELY), and by adding some organic
fertilizer, then you have a shot at restoring the soil's health.
Similarly repeated or regular applications of a fungicide will kill out
some (all??) of the beneficial fungi required for good soil health.

If you ever think you have an insect issue in the lawn, they are usually very easy to identify and treat as needed. When
I stopped using all chemicals on the lawn and started using only
organic fertilizers and products, I saw a lot of issues go away. In
addition to finally getting a green, dense lawn, my insect issues
disappeared. I used to have a mess of pill bugs (wood lice). They were
so thick they piled up on themselves. When I stopped using the chemicals the pill bugs disappeared. I had roaches in the lawn, too, but not any more. So it was an easy conversion for me to go organic.

Yeah they come every 2 months not 2 weeks. Your 1st sentence was correct not the 2nd (prob a typo). When they do come they leave reports of what was done, i.e. Fertilizer, insecticide, fungicide, weed control, nutrients, etc. my neighbor across st has them too on the same schedule and their lawn is looking great. They never do anything beyond treatment, mowing (and they mow much shorter than me) and once/wk waterings. They also do not have an oak tree in their yard, meaning they get more full sun time than mine.

I agree about going organic, but no place locally sells corn meal (except gluten stuff). And buying the chemicals at box stores + time applying it comes out close to the same as what I pay now for pest control service.

it been raining here past few days, used moisture tester (1 dry 5 wet) it's a 2. Neighbors get a consistent 3-4. So not holding moisture very well?

Can you provide with a online source for organic products or what your application schedule you use?

Were you able to figure out what the issue is? Having the same issue with my lawn currently