Smooth plaster turned into sandpaper

My 3 yr. old concrete pool has what looks like rock salt all over the plaster. I had the water tested by two different pool stores and both said it looked normal except the ph was 8.0 which I expected after sitting all winter, it was 7.3 when I closed it in Sept. What can I do to get it off and why did this happen??? If the only solution is acid wash can someone post basic instructions. I am a heavy duty diy'er. Thx for any help.

Do not acid wash the plaster it will just eat at the finish. The best solution is to polish the finish with a pneumatic diamond polisher or a waterfed diamond polisher.