If I wanted to ask about the thing or things that made my son's clothes dirty, what would I say?

I know *dirty* works as a verb, but when I said:

> What dirtied your clothes?

It didn't strike me as a natural sentence, so I googled the question (with quotation marks) to be sure, but got [zero results](https://www.google.com.eg/search?ei=_gOvW59JhM3AAobJn9gM&q=%22what+dirtied+your+clothes%3F%22&oq=%22what+dirtied+your+clothes%3F%22&gs_l=psy-ab.3...6277.13934.0.16743.10.10.0.0.0.0.222.1367.0j7j1.8.0....0...1c.1.64.psy-ab..2.1.216...0i8i7i30k1.0.rri45tz3kz0). That's when I realized this question format is not how you would ask about the reason for dirty clothes. I know there could be many ways to ask the same question. For example:

> Why are your clothes dirty?

I want to know the common and natural way of asking about this.