Audio Horizons fuses.... won’t buy them again...

Obviously, no storms, surges, nothing strange happened.

As for voltage surges how would you know? Not all voltage surges are caused by storms.

I notice the input voltage rating for the amps is 115Vac.
What is the avg mains AC voltage at your residence? Is it stable or does it fluctuate?
Does it ever get above 126V?
What was the voltage at the mains power receptacle outlets the day you powered up the amps and the AH fuses blew? I doubt if you know...... Who checks such things.

Am I defending the Audio Horizons fuses? NO. Just giving the guy at AH the benefit of doubt.
Just a guess the 5 amp OEM slow blow fuses that came with the amps have a longer lag, delay, time than the AH fuses.

If the amps are still under manufacture warranty you might want to check with the manufacture about using aftermarket fuses in the amp, in place of the OEM fuses that is spec’d by the manufacture. Especially tube amps.

Use of any other than Rogue Audio factory parts may void this warranty.

http://www.rogueaudio.com/documents/ApolloManual.pdf

PADIS are ISO certified and I believe HiFi Tuning fuses are as well. I would venture to say, without looking it up, that all fuses made in Germany are ISO certified or they wouldn't be sold. They have their standards as well as us.

All the best,
Nonoise

If only one in 10,000 fails why is the warranty only one month? Only in audio and politics do you find these kinds of disconnects.

If voltage variation was the problem, why didn’t the AH fuses in my speakers (always ON), did not blow?

Different deal completely. The fuses in your speakers protect the speakers from excessive output from your amplifier. If the power supply fuse in your amplifier blows it is not outputting any power at all and so will not blow the speaker fuses.