When I started up the pool, my DE filter was reading a pressure of 7 psi. That was when the pool was dirty after pulling the cover off. After filtering the pool, then attaching the Zodiac pressure vacuum and cleaning up the debris on the floor of the pool, the pressure when DOWN to 5 psi Now, five days later, the pressure is 4 psi. What the heck is going on? Could it be I need more DE in the filter? I expected the pressure to go UP after filtering all the dirt from the pool (it wasn't that dirty, but still). I also notice that the vacumm isn't working as well now either.