Chris, it may have been sunburn at first, and a bacterial / fungal infection set in because of the damaged tissue. Try spraying with Physan or RD-40 (don't get any on the flowers!) or use Listerine to wipe the leaves down top and bottom then spray with Neem or another fungicide that's usable for ornamentals. (Paphraguy uses cinnamon as a fungicide; you might try that first if you don't like using poison.)
And welcome to the boards!