it seems like my N7 keyboard layout keeps changing all of a sudden?

[freedda]

A few minutes ago I was typing a search in chrome and I noticed the bottom row on my keyboard had changed: to the right of the 'm' key was a dash where there used to be a parenthases like '. I went to the email app and started to type an email and noticed the same thing. However, while I'm typing this, the keyboard has returned to 'normal' and the parenthesis is back where it should be.

I've never noticed this changing keyboard layout before and I wonder what is causing it. ????