Following the soil recommendations and other tips in my original thread (https://www.houzz.com/discussions/good-yard-slowly-going-bad-help-needed-with-logan-lab-soil-test-dsvw-vd~3693709), my lawn is looking great this season! The green is clearly the deepest smoothest green in the neighborhood, and I'm sure that has a lot to do with the soil's improved ability to use the nutrients.

I also had a company come in and level the lawn. I should probably do a separate thread on that, but short version: I'm happy with the results so far, even though they used river sand. The pic above was taken only 10 days after the sand went down.

Thanks everyone!