Has a soil test been done of late? Sooner than 6 years ago?
The only thing that could cause a lawn to "suddenly" go bad is lack of adequate water, ie. the grass has determined it needs to go dormant because of the heat and dryness. Other problems (diseases and insects) develop over a fairly long period of time even though we may not notice them until "suddenly" it appears as a problem.

Not nitrogen starvation -- much more likely to be a case of nitrogen over-application.

Cool season turf grasses - and in zone 6, cool season grasses are most prevalent so assume that's what you've got going - do not benefit from summer fertilization. In fact, it is often detrimental to the health of the lawn, particularly a high N formulation. The lawn is unable to adequately metabolize the nutrients, it becomes stressed, requires far more moisture than typical and becomes patchy, scorched looking and browns out.

Frequent applications of a high N organic and therefore slow release fert during the primary growing season is causing your problem. Couple that with very infrequent, deep waterings (a must with that much N going on) and the grass cycling/mulching activity every time you mow and "good lawn mom" has become an overfeeding, water withholding monster :-)) Remember, the more you fertilize in spring and summer, the more you need to water.

Couple of other thoughts: your mulch mowing activity is distributing a decent amount of N on an ongoing basis and can supply upto 85% or so of any nutrient requirements your lawn needs. So you can back off on your supplemental fertilization. And most soil tests WILL specify a lack of nitrogen - it is the most mobile of all plant nutrients and extremely difficult to measure accurately and is almost always necessary to add. But in moderation and preferably via OM, which the grass cycling provides handily.

If you DO feel a need to supplement with an organic fert, by far the best time to do so is in fall. Less so in spring and certainly not at all in summer. There is far less need to water regularly, the lawn will be in active growth (as opposed to summer semi-dormancy) and will metabolize nutrients properly, preps the lawn nicely for winter and builds energy reserves to get spring growth off to a good start.

I'd consider some routine fall maintenance and an over seeding to fill in any bare or dead patches. And cut back on that N next season!!

I seriously doubt that applications of soybean and alfalfa meal would be the cause of this problem since the Nitrogen in them is not all that readily available.

Doubt all you want. It doesn't change the accuracy of my statement.

Let me blunt here.......kimmsr, you really do not know what you are talking about. For one, the N content of alfalfa meal can be extremely fast acting, which is why it is suggested avoiding any direct contact with plant roots. Second, any type of fertilizing of cool season grasses in summer is not advised..........for precisely the reasons the OP described and I outlined previously.

I do horticultural consultation for a living and have taught extensively in this area..........I DO know what I am talking about.

Kimmsr and Gardengal ~ I very much appreciate both of your responses and can better understand where I've gone wrong.

For one, I have been heavy-handed with the soybean meal and alfalfa and have to admit that I started seeing the problem soon after a hefty application of the later was applied in early August. Before that, the grass was beautiful. In fact, I can still see pellets in the flower beds where I also have experienced 'brown out' of some groundcover type plants. Can't imagine why these have not broken down as they have in years past. Sure causing me to hesitate ever using alfalfa pellets again.

In addition, I always felt that it was best to 'feed the herd' during the really warm months when activity was highest, but guess that would apply to fall as well. I also always thought you couldn't 'over due' with organics. Found out the hard way a few years and some spilled soybean meal later that one sure way to draw flies and create the 'stink of death' right outside your door was to over feed with soybean meal. I'm such a work in progress . . .

Kimmsr, based on what I have experienced, I can see where Gardengal is coming from. As to your comments on underwatering, I'm right there with you. I really slacked off this summer. Re: the soil sample, it was done this spring and all was good except nitrogen.

I'm in the process of daily watering of a nice Trifecta fescue seed blend and hope the yard comes back to life. Next up - make some serious notes for next year regarding lawn care ! Water well once a week if no rain and especially if slight browning begins to occur, continue mulch mowing and, if needed, apply a little soybean meal in fall. Got it.

Thanks, guys ! I can always count on my gardenweb family.

Given that the nutrient analysis of Alfalfa is in the 2-1-2 to 3-1-3 range it would need to be a fairly heavy application to cause Nitrogen burn while Soybean meal, at 7-2-1, would be more likely but would still need a fairly heavy application to cause that. More likely a combination of heavy applications of something with a high amount of N and lack of water could be a probable cause of the problem.
Hopefully you will be able to find a source of organic soybean meal and not use the genetically engineered product.