Lawn help

Lawn help

Hopefully some lawn junkies can help me out! Any ideas what this dead patch could be and the best way to treat it? This area has gone brown/dormant ever since we moved in three years ago. There's another more widespread, less defined area that also goes dormant very early in another area. I think the brighter green patch below the brown patch is from water run-off from a new tree that's there, but from the shape of this I can't believe it's just a water issue? I've looked for buried construction junk and treasure but haven't found anything. The ground there is surprisingly sandy clay stuff, so would adding topsoil and reseeding in the fall help? (what's the best way to spread top soil anyway?) Or does this look more like a fungus/bug problem? I'm not completely anti-chemical but I am careful about them and don't want to use more than necessary. I've been using the Menards grass treatments (preemergent so far, running behind on the weed n feed, summerguard, or winterizer) and I did a bug spray last year when leafhoppers and who knows what else were devastating the grass. The rest of the lawn has a lot more yellow blades of grass throughout than usual and I am worried there's some other issue going on with that. dead spot in lawn For scale, the fence in the background is 4' tall. Click on the image and 'all sizes' for a larger pic. (and yes I need to mow!)
oh dear…

oh dear…

FINALLY!

FINALLY!

Please tell me what this plant is?

Please tell me what this plant is?

Flower Pictures

Flower Pictures

Aprons

Aprons

My terrace again

My terrace again