So I suggested this in class and it was declared wrong with, "What happened to some of those?" as a replacement. Are sentences like the one in the headline strictly wrong or do they just sound bad?
So this is mostly about forming questions with become as the verb. We had a text about derelict houses that got restored, some of which became museums and activity centres. We then should formulate basic questions based on this text and the headline was the one I suggested.
As stated by my teacher this one is wrong and English speakers avoid using questions with become as much as possible. "What happened to them" was declared the correct version.