have canna cleopatra planted in area where it gets sun

starting at about 1pm and then for rest of afternoon.

they bloom fine here, but get browning on their leaves.

it's a flat browning, not pimply like i've seen in rust

on hollyhocks. it starts as a small lesion and then

encompasses entire leaf, and spreads to other leaves.

can anyone help me identify problem and offer suggestion

on how to cope.

thanks.