Clementine (butterfly) died. She was dead when I got to the tank in the morning. Everybody else was "okay" to "normal" except George (blenny) who was breathing very heavy. When I got home after the tank build, George was dead. All other fish; 2 clownfish, 2 pipefish, 1 mandarin, 1 randalls goby, and 1 gumdrop coral croucher are all fine. I just did a 15g water change and I am making more RODI water right now. I have also been adding in nitrifying bacteria to help deal with the die off from the fish. Smaug (cucumber) was still alive when I got home, but very obviously dying, so I put him in the freezer.
Despite how absolutely horrible this has been, unfortunately it could have been A LOT worse. It is only due to me having RODI water and carbon on hand, and catching it REALLY early that I was able to save anyone.