I have an 18 month old 1200 gallon in-ground bromine spa-ool. I maintain the spa-ool using the BBB method. We went overseas on vacation for 3 weeks and I asked a friend who has had his own pool(s) for many years to visit each week and just add 4 cups of chlorine bleach and about 8 oz. of muriatic to maintain the bromine level and pH/alkalinity. The reason for the muriatic is that I have a waterfall and the pH usually rises over a 7 day period.
When we returned from our trip, judging by the amount of chlorine bleach and muriatic I had left our friend, he had not added anything to the spa-ool. He does not test his own pool but relies on the clarity of the water as his guide. I now think perhaps he applied that same logic (or lack thereof) to my spa-ool which is why he did not add any bleach or muriatic in our absence. When I tested the water, the pH was way down at 6.8 (maybe lower) and the alkalinity was around 30! I adjusted the water balance back to a pH of 7.6 and alkalinity to around 90. Bromine/chlorine was also low - although the floating brominator helped - so I also shocked the spa-ool to raise the bromine/chlorine level.
The reason I am posting is that the spa-ool has a Pebble Tec finish and the plaster in which the tiny pebbles are embedded was beige (color known as Sandy Beach). After returning from vacation the plaster in which the pebbles are embedded has changed color to a turquoise blue. We have scrubbed the walls and floor with a hard brush, and while some debris seems to come off, the plaster itself still remains blue.
Can anyone suggest why the beige plaster turned blue? And is there any way to restore it to beige?