I just got my pool built a little less than a year ago and I noticed a few weeks ago this green stuff growing all over the pebble. The pool man added a bunch of chlorine a week ago but not change. Pool man isn’t sure what it is either. I’m worried maybe it’s a metal of some kind oxidizing in the pebble? I did see it growing on the grout too. Hard to see in pictures but if you zoom you can see it. Anyone have ideas of what this could be and how to cure? Thank you!!!