Eric

Brent's right about the wall facilitating leaf-burn. Ya might want to find a way to darken that section of the wall to prevent that. The leaves folding, the way they are, also traps heat & increases leaf burn.
Also in the news, had a long talk with the gardener this morning. He thinks it might be a calcium deficiency, if not just simple leaf burn. He treated mine by adding calcium and spraying the leaves with water daily to "cool" them down.
All in all, if the measures you decide on seem ineffective, I'd say Bob's probably right: Call a local Cooperative Extension Service - They can be Very friendly & helpful.
Will check into this more.