It seems unlikely that both tweeters went out at the same, time, but it is certainly possible if you got careless with the volume.
To find out if it IS the crossover, open up the speakers and put an AC voltmeter across the tweeter terminals, right at the tweeter.
If you turn up the sound and there is NO voltage across the tweeter, either the tweeter is shorted out or it is the crossover.
If there IS voltage, then the tweeter must be burnt out.
If there is no voltage across the tweeter, disconnect its wires from it and check its coil resistance with an ohmmeter. It should read between 6 and 26 ohms. If it is very low, it is bad. To be certain, connect a signal generator to the tweeter and turn it up to about 1 volt at an appropriate frequency to see if sound comes out or not.
Replacement parts should come from the speaker manufacturer in order to get matching parts.
If this is not possible, PartsConnexion has people who are very knowledgeable and they have an extensive line of crossover parts and can help you.