After staring at it in amazement, we had to consider how to solve this problem. We found oil and scum clumper at the pool store, followed by a liquid enzyme that is supposed to break the clumps down so the filter can handle them. It's working ok so far, but each afternoon, we get another down-pour that spreads the oil all over the backyard and back into the pool. I'm not sure how we'll clean the deck when this is all over.
Sadly, the plants affected will have to be removed. There is a kill off already. I do have some ideas for the back though - guess the time to start that project has come! Sheesh!