I had my roof replaced, and during the process some roofing nails got into the pool and left some rust spots. Unfortunately, the roofer decided to try to remove the spots and used a brush (some sort of metal I assume). There is one spot where he really scrubbed, and now there is more aggregate exposed in that area making it look darker. The finish is a little over 2 months old. I stopped the roofer as soon as I saw this, and had the PB come over. He removed remaining stains with acid, and put some acid on this darker spot to try to blend it out a little. There is still a noticeable spot. Does anyone have experience with something like this? Does the white cement tend to keep coming off with time exposing more aggregate?