Algae loves phosphates and nitrates. They are a part of every tank and we all have algae. Your RODI should be taking care of any copper, You can always get a TDS meter and test the water coming out of the RODI system. It is likely not copper if you are using RODI though. The only products I would use to combat algae as far as chemically or bottled would be a bacteria supplement. The bacteria supplement would work just by using up the nutrients faster or out competing the algae for resources. You already reduced the light time which will help for sure, just be sure your corals respond accordingly. If it were me I would test my water and if it looks good then hop on over to your LFS and see what they have as far as trochus, turbos. You can also go with a tuxedo urchin. They are algae eating machines, but they will munch on coralline algae as well. The companies Dr. Tims, Brightwell, and Fritz all offer bacteria supplements.