Large colonies died over night abhh

[Finnegan]

So woke up today to find my large birds nest colonie almost bleach white and about 1/3 my acro also took a huge beating. I have not touched anything for a few days and water change isn't due for another 2 days....
The only thing I can think of is my room mate dumped something into the tank. Is there any other reasons besides sabbatoge that a volleyball size colonie would die over night??