We recently had our pool replastered and the waterline tile replaced. The grout was white when installed (like 3 weeks ago). Now, wherever it's exposed to water, it is yellow! Please see pic. Any ideas as to what's causing this? It started to look very slightly yellow right away, but I figured maybe that's just what it's supposed to look like when wet. Now it's REALLY yellow.
If it matters, we've had a pool guy doing our start up (regular start up, not a hot start) and he was coming out a few times per week for the first 2 weeks. No one came last week because our guy is on vacation. The water turned a little green, and on his advice (we texted him) he said to add algaecide, which solved the water problem. I understand algae can stain, but this is yellow, not green, and when we scrub it nothing happens. Our water wasn't even very green, just a little bit. And our water has been back to blue for a week now, but the grout is still yellow! Help!
This is a pic inside the mouth of the skimmer. The parts underwater are yellow and the parts out of water are white. The yellowing is not confined to the skimmer though. It appears to be anywhere the grout is under water.