No ammonia, no nitrites, nitrates are 30ppm. Temp is 78, CO2 beyond 30 ppm, and oxygen is plentiful as plants are pearling like crazy. Not testing pH as I know it is low, around 6. I inject CO2 and keep lights on 6 hours a day and feed once per day. Just had a GBR die... the seemingly healthy one. It went belly up in a matter of minutes. Earlier today it was nibbling at food but spitting it back out and all of my fish have been reclusive. I had to relocate all 4 of my otos to another tank as well as one glowlight tetra that was swimming upside down and sinking. I'm not expecting them to be alive tomorrow... I have not dosed ferts in 3 days and just did a 50% water change yesterday, I don't understand why everything is going wrong. I have also been dosing Metroplex so it shouldn't be a parasite, but haven't dosed that in a couple of days either. I know my nitrates are probably a bit too high, but they are close to being in the safe range. I rescaped/replanted the tank recently and added two pieces of wood, but one I boiled for almost 2 hours and the other I scrubbed with scalding hot water since it was too long to fit in the pot. Neither show any signs of fungus or mold. I have added prime and stability as a way to try to combat whatever it is doing this to my fish. I have not used chemicals around the tank, burned anything like candles, or used aerosols. Please help!