It’s not temperature, water flow, light, salt, no new additions, no pesticides are used in the room. Everything was literally perfect and thriving yesterday, I’ve had anything happen so dramatically in such a short amount of timeSounds like a bloom of some sort and likely bacterial. You mention corals suddenly bleaching. First thing to check is water temp. High temps will cause tissue release and RTN. Increased temperatures will either modify the structure of the coral microbial symbiotic community or trigger the production of factors affecting the tissue.
Typical actions that cause sudden bleaching and tissue loss are :
- Alkalinity spike
- Temperature spike
- Salinity spike
- Low dissolved oxygen
- Poor water quality related with phosphate levels up to 5 ppm
- Change in water flow
- Addition of sand
- Changes in brand of salt
- Bad test kits giving faulty results
- Levels of minor elements such as Iodine, Potassium, Strontium
- Light intensity or sunlight hitting tank
- - Changes in water flow
- Addition of new corals
- - Pesticides used in the room