I'm glad to see that the sisters finally punished the wilder new members. I disagree with how it was done, though. The sisters should have voiced their concerns in general terms to a full new member meeting, without naming names, and then their standards board (or equivalent) should have had private meetings with each new member in question. Jessica should not have been told "you're not in trouble but all your housemates are."
We know they spoke to Jordan privately earlier on. Did the other new members have any inkling that their behavior was causing concern among the sisters? Or was it just "surprise, we're taking points away from you"?
Jordan did have a point, though, that they were out celebrating Candace's 21st, which is a one-time occurrence - so getting somewhat wild should be acceptable. (Note that I say "somewhat" - they were over the top.)
As far as age goes, I think Dede is the only new member in the house who's underage throughout the show.
I, too, am disappointed (but not surprised) that MTV didn't play up other aspects of sorority life. They had a great opportunity to talk about Mitzvah Day, but all we heard was "she's doing community service, we're un-mitzvah-y, giggle giggle."

But talking about community service doesn't bring you ratings... showing the girls getting piss drunk and dancing in bars brings you ratings.
You know what scares me most about this show? The fact that I seem to be addicted...!