Two weeks ago I fired up the pool like I've always done. Got most of the leaves out with the net to the point where I could run the robot. I typically do not add DE right at opening because I know that I'm going to pull the grids and hose them off after the water looks clean. Filter gauge was showing about 20 psi at start up which is normal. Yesterday the pool is clean and looking good and the grid pressure is reading 34 psi so it's time to pull the grids. I do so and hose off some really foul smelling worm remains, clean out the strainer basket and reinstall the grids (which looked pretty good). Pressure goes right back up to 30 - 32 psi.
I've done this before and never had an issue getting the pressure back into the low 20's. So I yanked the grids again and hosed them off more thoroughly with a better hose fitting. Reinstalled the grids and get the same thing. What am I doing wrong?