I don't know if you read the comments, but someone commented about the distinction between fish and veggie dashi. Maki's answer was:

The reasoning here is that most of the time, especially at restaurants, dashi is made with some kind of dried fish. That is the norm. If by chance the establishment you are at makes their dashi from vegetable ingredients only (which would be unusual) they should be able to tell you that once you've said you can't have dashi.