I'm not saying you were saying it went from 0-5ppm in an hour. But in the first few posts you implied it was the result of the water change. I'm just saying that it's almost definitely not the water change that caused this. There must be some underlying issue.
Have your filters both definitely come back on after each power cut?
And they wont have only affected your tin foils and ruby shark. It just affected them quickest and most extremely. I would expect some damage to have been done to the other fish depending on how long they were exposed.
As I said... what did you do after you read the test results? And when did the nitrites hit 0 again?
