I have an inground pool with Pentair DE filter. The pressure is registering very high. I forget the exact reading now, but it's about 10 lbs over what I would normally allow it to get to before backwashing or deep cleaning by taking the filter apart, so quite high. Everything I normally do doesn't help. Backwashing didn't help, so I took the filter apart and did a deep clean taking all the grids out. This also didn't help. Next I followed advice I found online and soaked the grids in TPS cleaner and ?? something acid. That didn't help. I noticed what looked like a small crack on the manifold so I replaced it. That didn't help. I replaced the pressure guage. That didn't help. What next? I hate to spend $200 replacing grids, especially if that also doesn't help. any advice for me would be deeply appreciated. Thanks.