If you really have a Cu problem, restart your tank may be a solution. Several times dilution for your system can reduce the concentration of Cu under the detect limit. And, It is convenient to buy artificial rock or live rock in Taiwan and wont cost a lot. But IMHO, since your fish and LPS can live in your tank, I will try to keep working on making the parameters stable and try improving the system. Then try SPS again later. I agree danmhippo that the reason should be the water parameters, not toxic such as heavy metal.
About "organism", maybe it should be called "nutrients" in English(please excuse my poor English). As I know, deep red coralline means your system is not strong enough to remove nutrients in the tank, so the nutrients are in high concentration. It might be a way for you to improve.