Hi again

Well it sounds like it's not percipitate. Likely then to be dead algae.

Have you tried the DE trick. Assuming your filter is sand, do a good backwash, the set it on "filter" again and note carefully the pressure. Then add some DE to the skimmer a cup at a time. When the pressure has gone up by 1 PSI, stop adding DE and let it run. Should clear it up over night.

Good luck with the leak.