Bacterial blooms (if indeed that was it) are best fought with UV. Water changes help, but not much since the bacteria are actively reproducing. The fact younger nitrite isn’t necessarily indicative of a cycle, but that something is dead/dying and creating nitrite. The coral you have (gorgonian) needs a more mature tank, and others are heavy mucus and toxin producing when irritated, so that’s going to mess with your system. Carbon though a reactor is the full time solution if you are going to keep these types specimens.