this is fairly dumb/brute force... but,
turn the monitor level up loud so that you're hearing the system hiss a bit...
then just cover the tweeter with your hand and remove it and cover it and remove it and so on...
you should hear the high hiss come and go noticeably.
Do both tweeters sound the same?
If one hisses and the other doesn't....

Play a percussion track on speakers. If tweeter is OK the sound will be good, if any of them is blown you can find it easly.

thanks