Hello all, I have a problem with my tank, 1 and a half year old 300L (80 gal), everything was going great for a few months when all of a sudden, my alk dipped under 5 dkh and corals didnt look good, obv. No3 also dipped to 0 from 10... In an attempt to save it from this situation i did a 50% water change and started dosing some kh. I somehow managed to overdose it with my pump to the point it was 12 dkh (was not home that week, im an idiot i know). So i quickly managed to do a 30% water change that got it to 9.5 dkh. Since then, i have not messed with it and let it stabilize. All params are ok except no3 which is still in the range of 0-2 ppm. I will attach some photos below. Sps lost tissue in the lower light/flow parts mainly the middle, one of my acros became white on the tips and died, the other ones polyps are ok but the body is bleaching slowly, one of my montis just died in the span of a few days even tho it looked ok before, other montis are starting to die aswell, seriatopora are dying from the middle, lost volor and polyp extension, chalices slowly died, one of my duncans ejected its polyps, the other looks a little bothered. Favias and goniastreas lost some tissues on the edges. I really dont understand anymore. Params are all ok now but they are still dying.