Septic tank leach lines?

Leaklng irrigation system?

Improper fertilization?

no septic...
leaking irrigation lines; always a possibility.
improper fertilization; have had the same guy doing my lawn for 4 yrs and never had it look like this.

why would you suspect leaking irrigation lines?

There are a lot of possibilities: disease, insects, nutrients and water. Process is to eliminate them one by one. Start out by seeing how far you can push a screw driver into the soil in a number of places. Distinquish areas between the lighter and darker areas for testing.
Look closely at the green grass at the transition areas between the green and straw colored turrf for signs of lesions and insects.
Do you know what your service has applied this year and when?

My first inclination is water or disease based on the pattern.

Here is a link that might be useful: Guide

Do you see a giant ring of green grass? It is bigger than your pool out there. That is caused by a fungus. It seems to be fertilizing the lawn and making it deeper green and more dense. It is probably growing faster there, too.

Where do you live?

What kind of grass do you have?

How high/low do you mow?

When were the last two times you fertilized and what did you use?

How often do you water? How long do you water?

Have you used any herbicide, insecticide, or fungicide this year?

I've had white moths flying out of my lawn for 50 years. Don't worry about stuff that isn't doing any harm.

I should strongly urge you to resist using a fungicide simply because I mentioned that you have a fungus in your yard. The fungus is causing green grass. It very well could be the lack of fungus that is causing the yellowing. Ideally you would have 60,000 or 70,000 species of fungi in your soil. Applying a fungicide is certain to upset the balance of microbial nature, so if you could answer the questions before jumping to conclusions, it would be helpful.

I live in southeastern Massachusetts
originally seeded w/ Lesco Park & Athletics 5 yrs ago
overseeded the next 2-3 falls w/Park & Athletics.
Last fall overseeded w/ Lesco Teammates Plus

I mow at the highest setting on my tractor & my pushmower. I typically mulch my grass clippings till about 2-3 weeks ago when I 1st noticed a few spots of red thread and started using the pushmower so that I can collect the clippings.

May 29 and then returned on June 16 after I called regarding the moths and discolored lawn was the last times my lawn was serviced. I'm not sure what was used. I do recall him using 24d for some areas w/clover.

2 times a week running most zones for 30 mins.

I know of the 24D, not sure of pesticides and pretty positive that he hasn't use any fungicides.

Do you know if he uses liquid or dry fertilizer? If he only uses liquid, then I would apply a dry organic at your convenience. I like alfalfa pellets (rabbit chow) for the price and performance. Application rate is 20 pounds per 1,000 square feet. This time of year it is a little too warm to apply other chemical fertilizers. If you can find ordinary corn meal, then use that. It has other benefits which might make a difference.

It could be a water related issue. 2x per week is a lot more frequent than you need to water. I have parts of my Texas desert lawn that get watered 2x per year. Of course shade is a factor as is grass height, but certainly 2x per week is more than you should need. I would start to wean the grass off that watering schedule. If you have temps in the 80s then you should be deep watering about 2x per month. Deep means one full inch all at one time. Measure an inch with some cat food or tuna cans spread around the yard. Time how long it takes to fill them and water for that time. When the temps get into the 90s, then go to 1x per week watering. But get to that point gradually. Your grass is not ready to go cold turkey.