What kind of grass is it, how low do you mow it? It looks pretty short. Pretty shady most of the day, I'm assuming?

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You have proved these levels of pH?
What tool did you use to arrive at these readings. Can they be trusted to be accurate?

From area to area you have 3 different pH levels that are quite different from one another. Its quite unusual for areas that are not that far distant to have such disparate of readings.
I think you already have the answer --the pH at 7.0 --neutral reading, proved the best.
Most grasses do well when the pH is more close to the neutral side....either above or below.
If you can rely on such readings, then its a simple matter to bring up the pH to more a neutral level with the adding of horticulture lime.
You might look into the use of gypsum---it can raise low acidity and lower high acidity.

Aside from the affects of the pH, there are any number of reasons why an area of grass turns brown. From bugs, to low moisture content, (not watering enought), to too high moisture content (too much water given)....which can cause short roots--opening up the grass to hot sun drying it out)
to mowing too short--causing much the same as above.
To disease and to bugs that are eating the roots.

One other thought; the dark color seems to point out you are fertilizing the areas. I'll assume you are regularly feeding the areas with a high nitrogen content fertilizer---usually early in spring and follow-ups throught he seasons.
Too much fertilizer will, of course, bring the pH skywards....i.e....too high in the acidness side. (below 7.0) The 5.0 and 4.0 readings points out this possibility.
High nitrogen fertilizers, applied year after year, after year....with no check on how much is spread and how often, sooner or later catches up to a lawn.

"What tool did you use to arrive at these readings"

Mosser Lee

No fertilizer since late March. Well, I did sprinkle some leftover starter fertilizer back in late May. No bug problems to speak of. Area #3 has actually improved since the photos above were taken July 9. Not sure if it's the cooler weather here in North Georgia or the Scotts Fungus control applied twice this month two weeks apart...maybe both.

If any area gets the most moisture it would be area #2 on the right side of the walkway to the creek. It gets quite a bit of drainage.

Yes I added lime a few weeks ago...160 lbs for 2,400 square feet. I left area #1 alone and did not add the lime pellets.

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It's the first year for the lawn so I am happy. Big difference from last year(below) I had an idea Ph was the key, yet it's seldom talked about. It's more like the big lawn product companies would rather see idiots like myself buy unnecessary stuff, or when problems get too severe.

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It was basically a swamp...and overgrown with weeds.

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Looking forward to aerating in a month or so. I understand that helps quite a bit as well. Some areas were quite compacted by tractor movement and I really didn't prepare the soil the way I should have.

Thanks for the response. As you can see I'm a newbie to this stuff.

Here is a link that might be useful: Lawn Progress From Start

I wish I had that backyard with all the trees back there. I'm jealous.

Sorry I don't have anything useful to provide since my grass grows on limestone rubbles. Very alkaline soil... I can't even lower pH at all with all that limestone.

Thanks Lou:

I get compliments all the time on the setting. I'm just so thankful I had a patient real estate guy that helped me find this place. I actually took out 30 trees a few years ago. It was definetly "in the woods." So bad it was actually chilly in the summer months with the shade and dampness from the creek.

Thinking about what jeannie said...

"Its quite unusual for areas that are not that far distant to have such disparate of readings."

The reason for the difference in the three areas.

#1- When the stone walls were built last fall the masons did all their concrete mixing in the area, allowing all sorts of good nutients to soak into the soil over the winter months before planting. Soil was also brought in before like #2

#2- Was basically soil brought in from a bank on the other side of the house. No amendments were added before planting. I was in too much of a rush...didn't use starter fertilizer either.

#3- I never had planned on planting grass here(brown area). It's the original soil that was covered by years and years of leaf decay. Highly acidic?

Some pics don't show for some reason. Maybe blogger doesn't allow hot linking of photos?