What has blown my tweeter????

It's not clear what you mean when you say the tweeters have totally disappeared. If they look normal but just aren't playing, you could have a component failure in the crossover or a bad wire connection inside the speaker. Or you could just have a poorly manufactured tweeter that failed after some use.

If you really mean that the tweeter is no longer visible to the eye, i.e., that it has been physically removed, then it must either have been ejected across the room or have fallen into the speaker enclosure. The volume settings you described are unlikely to have caused this. Was there a thunder storm? A close lightning strike can do weird things. Otherwise, I would suspect foul play. I assume the tweeter was in place when you got the speakers. When was the last time you observed the tweeter? Do a lot of people have access to your listening room? I hope you find out; good luck.

There was a DIY post recently about building your own speakers. I would search for that and then track down all who expressed an interest. One of them has your tweeter! It's very obvious. Trust me on this.

I also would refer you to several recent threads regarding the known hazard domestic cats pose to stereo equipment. Cats have been observed lying on amplifiers and sitting/crouching on top of speakers. If a cat or pair of cats has had access to your listening room, you should sequester and interrogate it/them. Quite possibly one of them or even a whole gang has made off with the tweeter. If you don't do something now, your woofer could be next.