Could be velvet - it kills fast...but not that fast.
When was the last time you looked at your fish?...if it were the day before they died and they ate and did not look sick - its not velvet...you can miss the "spots" with velvet - but the fish will look dusty or filmy...their color will be pale or off and they are clearly in distress...they won't eat...when their eyes cloud...they're pretty much gone...its fast...but you would have noticed the day before.
Anyone spray air freshener in the room? Use beach or another cleaaner in an adjacent room? Replace a filter sock? Feed something different? Use carpet fresh and vaccume? Is the tank open or covered? Skimmer or without?
When was the last time you looked at your fish?...if it were the day before they died and they ate and did not look sick - its not velvet...you can miss the "spots" with velvet - but the fish will look dusty or filmy...their color will be pale or off and they are clearly in distress...they won't eat...when their eyes cloud...they're pretty much gone...its fast...but you would have noticed the day before.
Anyone spray air freshener in the room? Use beach or another cleaaner in an adjacent room? Replace a filter sock? Feed something different? Use carpet fresh and vaccume? Is the tank open or covered? Skimmer or without?