What makes fish have a few darting spasms right before death?

[FlyPenFly]

I just had 3 fish die identical deaths. They jumped around the tank in a crazy energetic way then died a few minutes later. Kind of like a final hyper energetic spasms. They were struggling 24 hours right before the death.

 

[namxas]

What species were the fish?
How long did you have them?
Were they from the same source?

Anything else affected?

 

[evolved]

Stray voltage?

 

[JohnniG]

Sounds weird