Gray Mottling=Plaster discoloration. New plaster 8 months ago. Always followed BBB method. Finally got contractor to take a look at why pool plaster has lots of discoloration. Never added Borate, didn't think it was necessary. Only fill pool with city water.
Test water 5x week, 1x month compare to pool store results.
Not sure if contractor is making excuses to get out of crappy install with plaster mix.
Current test results:
Alkalinity=my results 70, his testing 45
cooper=his testing 0.1
iron=his testing 0.2
Here is the report, you have what the NPC calls the deadly duo, both low alkalinity and high calcium, this would certainly cause the look we are seeing and also cause the nodules to grow in the finish. I'd correct the chemistry as soon as possible to avoid further progression. Also there are no borates and you have a fair amount of iron in the pool. If you have any old reports like this one I'd like to see them.