It doesn’t look that bad from the pictures, but I wonder if you could play around with the direction of the Powerheads to point them more towards the affected areas. I have 5 ‘jets’ in my system so I created more flow towards the bottom of the tank as in my case it was mainly the sand and lower rocks that were affectedThanks that puts my mind at rest ...
I've just blown all my rocks off and aquavac the sand bed this is how my tank looks
But it's still in some places