You hit the nail on the head, chem. I added two ounces of cyanuric acid yesterday, and some of it was still sitting on the bottom of the tub this morning. I ran a 20 minute cycle right away, and the crystals seemed to disappear. My filters were orange from collecting all the rust out of the water, so I had to clean those out. I will just check the cya level in 5 days, and see where I sit.
Boy, there's nothing like a fresh fill with crystal clear water.