How do you know how the Chromis died?I just finished reading the thread and I was thinking... what if you don't have a chemistry problem, but something else. I mean... your rock looks so clean because of your big CUC (if I remember well, you have 7 hermits in your relatively small tank) and the Chromis were not killed by some other fish, but they had Uronema. This desease looks like small red patches on the skin. Maybe you should search on the net for pictures and see if it looks like what you saw on your fish. I mean
.. You didn't quarantine the fish and few days in copper at the LFS would not cure anything. Your nitrate problem would (should) be easily solved if you just buy a Brightwell NO3 export brick and seed it with bacteria. Or any other media that you would prefer (from seachem, maxspect etc). I just like the Brightwell because it has sulfur inside and you no longer need to carbon dose.
