i noticed that just 1 hour ago. GHQ changed.

Yeah the obtainable girls are changing, why? No clue. Once I realized how crappy the chance time rate was I decided to hang back in 9-6 and camp to ensure I didn't pass over any new SRs but today the obtainable girls in 9-6 are different. I just know I'm sure has hell not going back to the bonus stage until I got all the new girls. I'm guessing they'll continue to rotate the selection daily.
-EDIT-
Or maybe they won't. I have no clue. I'll wait until tomorrow before I assume too much.
-EDIT AGAIN-
OK now I've seen the GHQ...didn't realize what I think Skulkraken and chilinfar were talking about until I accidentally clicked on GHQ. Apparently the stage 3 girls have their own GHQ.