Elliot, just saw your post, and I see it was from a while back. So, what happened? Did you figure it out?

Looks like Thrips damage to me. They bite the plant in the summer than leave a virus which only appears many months later in some cases esp. bulbs and tubers. Try cutting back all the foliage and keep the tubers cold for several months if you don't already live in a cold winter area. As soon as new leaves appear in spring spray with Neem to stop the critturs coming back. Good luck - ian.

We get this type of occurence (possibly the same pest), every year with various perennials and shrubs, such as Philadelphus, Phlox and Rudbeckia.

We never see what causes it, but at a certain stage of growth (or time of the year), the leaves get twisted and distorted. After some time, new growth appears, which is unaffected, but we never get around to actually spraying the plants.