AJ, my appologies for my typo last night, I meant to suggest adding ~3.75 lbs of earth to the filter. It seems to me that you have a couple of lbs of de stuck in the filter, that backwashing can't remove. The best way to correct this would be to take apart the filter, and clean the grids with a garden hose. However, as you will be moving soon and have already invested too much time and money into the pool, let the new owners deal with it, but let them know of the possible problem (I was going to suggest a white lie for you to tell them, but doing so would be unethical). Glad that the problem has resolved, though
i can see it comming back until the old de is completely removed and the method I advocated earlier is regularly used. Again, sorry for the typo