What melted my tweeter?

We had a brief power flicker in the nighborhood and when I came home, there was a burnt electrical smell and a hum from my left speaker.
(I leave my gear on all day)

The tweeter makes no sound and is deformed, melted.
All the fuses in my amp are intact.
Speakers are under warranty but don't know if this will be covered.

I assume the power flicker is responsible but not sure.
I will be taking it in for service but thought someone here might have a clue what happened.