Chem geek; white deposits on gray plaster?

[geeman]

I am a plasterer in PA. I have a gray plastered pool; white cement, white marble, black Davis hydro-tint. The pool was plastered last July and according to the service guy he waited 28 days to add the salt and all chemical parameters have been kept within acceptable levels since. Besides normal marbling, starting in the fall, areas of the plaster started to develop very white marks mostly in the spa and some on the pool floor but the customer didn't call anybody at that time. The pool was closed for the winter and just re-opened. The rest of the pool still looks great. Transition areas around the tile are the worst, especially around the 4 main drains in the spa. I met the builder there and we drained the spa so that I could acid wash and sand the spa step. It took away most of the marks but the plaster still doesn't look like it did when first done. I saw this last year on another pool we did, this one gray with 3M Colorquartz, also a salt pool with a hard hit spa and pool floor. The builder thinks the plasterers may have used too much calcium in the mix. So, I asked him, "why is it only in the spa and pool floor?" He suggested that the higher temp in the spa has drawn out the calcium and has brought it to the surface. If that is the case I would assume that after acid washing and sanding the plaster would still be white underneath, not the original gray. The marks are smooth but can be removed with a razor blade (I have a small amount in a baggie and it looks like calcium scale). After removing the marks with a blade there is a slight recess in the plaster. I can also see lines made by a pool brush through some of the white but it is definitely not brushable now. Also, the metal ring around the light in the spa has gone from stainless to a dark bronzy color. He said his guys accidentally spilled acid on before we plastered but the discoloring is very consistent and I am wondering if the same thing that is causing the plaster to change is also affecting the ring. I will gladly drain, acid wash, and sand the whole spa but would like to know if you have any ideas as to what may be causing this discoloration/deposit. The builder is contacting the service guy to get his records. Thanks.

[seen it before]

it's the salt causing this problem, suggest after fixing plaster to run the pool without salt in pool & just normal chlorine etc. for 90 days or the same amount of time it took to see it start to happen in the pool.
Heck add waranty to cell when doing it so their happy.

it's not going to happen have seen issue before

[chem geek]

I don't have knowledge in this area so can't help you. It is true that calcium scale is more likely to form at higher temperatures.