Ash (wood ash) contains significant amounts of potash (potassium) and calcium carbonate (think lime).
Low potassium can result in increased disease susceptibility. Low K might account for the brown blades you have reported due to a disease and the noticeable difference you are seeing in the grass in the ash areas could be due to a lack of disease. Otherwise I don't know that added K would result in a significantly noticeable visual difference.
The PH sweet spot for nutrient availability is arguably thought to be between 6.3 and 6.8. Although a lower PH allows some nutrients to be more available, too acidic a soil can result in phosphorous deficiencies and a weak biomass (micro-organisms). Higher PH is conducive to a healthier biomass (but too high a PH can result in iron deficiencies.)
The question is which one(s) are you seeing being brought into play by the ash?
The only real way to know is to get a soil test.

Wow, what a response! Thank you!

I should have known better than to think it could be a "sure go ahead" or yes/no answer...

The area with ash is about a 5' x 7' area away from the main part of the yard that I've referenced earlier but definitely could be an indicator of something...

Thanks for the great info, I appreciate it!

Your welcome jacob. Those are the possibilities that came to my mind. I'm sure there are other, even more likely, possibilities that others might add.