HouTex,
Based on the plasterers chemical readings, the water is on the positive side of the CSI. It was not aggressive. If you allowed him (the plasterer) to do a No-drain, then your plaster WOULD shows signs of aggressive attack. The point being that you would no longer be able to prove that an "aggressive attack" didn't cause the spotting. You are right, the plasterer will probably fight you on this. He honestly may not know why "spotting" occurs on some of his plaster jobs, and has believed what other plaster people have told him. And of course, he doesn't want to pay for a replaster.

You water chemistry is excellent. As others have stated (I believe) on this forum, a CSI between -0.5 and +0.5 will provide very good balanced water for your plaster job. As you know, the higher calcium level offsets a lower TA. I would also allow the pH to rise a little (7.6 to 7.8), that is my personal preference and experience.

Finally, since your plaster also contains quartz and has a general mixed coloring aspect to it, the spots are not showing up very much (as you stated) and probably aren't serious as such, then I think you have nothing to worry about. The depth of the affected spots are probably only about .5 millimeter deep (the overall thickness of your plaster coat is probably about half an inch). Just understand that you didn't do anything to cause those spots to appear. There is nothing you have done or can do to have stopped this.

Maybe you can take a minute (or however long it takes) to educate your plasterer on what actually causes spotting to occur, and help prevent this from happening to others. If you ever want to puruse this, PM me and I will provide you some free advice and literature. Good Luck.
P.S. I hope Ping reads this too.

onBalance, thanks for your comments. I hope I don't need to take this any further.

Those numbers indicate that scaling is likely. The water would not be "aggressive" and would not etch the plaster.

I agree with OnBalance that this is spot etching due to defects in the application, and not due to improper chemistry.

What do you remember about the day the plaster was applied?

Is the plasterer a member of the National Plasterer's Council?

Even if they're not a member, you can still ask the NPC a question regarding the plaster, and even request an inspection.

http://www.npconline.org/mc/page.do?sit ... &orgId=npc (Find Member)

http://www.npconline.org/mc/page.do?sit ... &orgId=npc (Ask Question)

http://www.npconline.org/mc/page.do?sit ... &orgId=npc (Request Inspection)

The plaster was applied in early December 2010. IIRC, it was a warm day. There was no rain, but it was a humid day (not uncommon in Houston in December). I remember it took a long time (several hours) after the plaster was applied before they started to fill up the pool. Based on their reaction it seemed to take longer than usual to dry out enough to start adding water.

I recall now that some of the spots/marks on the tanning ledge showed up within a few days. Most of the spots showed up in about 4 months.

JamesW,
I appreciate your comments.
HouTex could contact the NPC. But I have to say, the NPC has been given several "failure analysis" studies by professional cement labs that have determined that "white spotting" is caused by improper plastering practices. The NPC has also been given cement studies and literature documenting that "gray mottling" discoloration is caused by the combination of high calcium chloride content and late hard troweling. As far as I know, the NPC has refused to acknowledge both of these studies and conclusions. In California and Arizona, the NPC Technical Advisor has been sent out (when customers have complained) and has conducted many inspections on white spotting and gray mottling discoloration problems, and every report I have seen, he has blamed aggressive water chemistry for both problems. Sometimes, onBalance has been called in for consultation and has been able to get the plasterer to redo the plaster job.