Are you using the 1/3rd rule? It's August, I normally have no problems keeping the yard looking tight mowing once a week. Normally, there are some Hot spots I can't afford to take care of with watering. Not this year though. If I go more then 4 days I'll be mowing close to half of the height of the grass and that leaves a buildup line on my mulching deck between the middle and right blade. Normally grass would eject out of the side port but with the Mulching insert in it has to settle back into the grass. With too much grass though it ends up on top.
Now this is just how the grass looks, have you checked to see if it's just discharge or if it's actual grass that's not been cut. Eventually he grass will go dormant and will keep up with it, throw the winterrizing fertilizer on and over seed. Throw the fertlizer on now, you'll be doing a reverse 1/3 rule. leaving only 1/3 of the grass.
