If you happen to mow when it is too long and the clippings collect on top, simply move over it again to chop them small enough to fall down through the uncut blades.

Watering: Deep and infrequent is the mantra for watering. This is for all turf grass all over the place. Deep means 1 inch all at one time. Put some cat food or tuna cans around the yard, and time how long it takes your sprinkler(s) to fill all the cans. Memorize that time. That will be the time you water from now on. My hose, sprinkler and water pressure takes 8 full hours to fill the cans. Your time will likely be less. I like gentle watering. As for watering frequency, that depends on the daytime air temperature. With temps in the 90s, deep water once per week. With temps in the 80s, deep water once every 2 weeks. With temps in the 70s, deep water once every 3 weeks. With temps below 70, deep water once a month. Note that you have to keep up with quickly changing temps in the spring and fall. This deep and infrequent schedule works in Phoenix and in Vermont, so it should work for you. The reason for deep and infrequent is to grow deeper, more drought resistant roots and to allow the soil to dry completely at the surface for several days before watering again. If it rains, reset your calendar to account for the rainfall.

Thanks for the advice on watering frequency.

I had another thought. Since the previous owner let the grass grow very long before mowing it for the last time, is it possible he shocked the grass by cutting off too much in his final cut. During our walkthrough the lawn was very long, but still very green. On move in day he had cut it to about half it's length. My understanding is that this is hard on the lawn.

If so, what can I do to bring it back? Just wait? Fertilize?

Mowing off more than 1/3 of the blade can for sure shock grass. It should recover from the shock on its own... if it was healthy prior to the low cut. Sounds like it was.

Your neighbor might not know what the previous owner did precisely. He might have assumed it was fertilizer. What if it was lime? Fungicide? Seed? Weed control? Or a pre-emergent? Don't assume and I would take what the neighbor said with a grain of salt. My neighbors see my applying stuff just about every week or so... and most of the time, it's NOT fertilizer.

Best bet: wait 2 more weeks and see if it is still yellowing. That should bring you to about a month after you move down in, yeah? If so, you're probably in the safe range to fertilize.

I would hold off on any other types of treatments (weed preventer, fungicide, weed killer, etc.) until the spring. Just to be safe... for the same reasons listed above. You don't know what the previous owner has already applied and whether applying more might unknowingly put you over thr limit.

By the way if the previous owner cared for the lawn right up to move-in day, you're ahead of 99% of new home owners. Usually it gets neglected for months prior to move-in.

I think you are watering way too frequently and not deep enough. Too frequently will cause yellowing in almost every kind of grass.