Whodunnit? Killer update!

I have a little update that I found from the killer on twitter. Apparently, there was a clue as to the killer's identity during the champagne meeting at the beginning of the episode.

I watched that part over and over, and I'm almost convinced that this clue occurred immediately after Sheri dropped her champagne glass. Unless, of course, it's an extremely subtle clue that no one will understand until the killer is revealed. Here are my theories:

#1: After Sheri drops her glass, everyone is chattering loudly and laughing and joking about her dropping it. I feel like something might have been said that was a subtle hint. And I really couldn't make out much except for Don kinda heckling her about dropping it. This, of course, may be it. What if Don is the killer and him jokingly heckling her is the clue? An interesting idea...

#2: It's something much more subtle that something someone said or did, that really won't become clear until we actually know who the killer is. I'm not going to try to analyze this, because I clearly won't figure it out until much later.

#3: Possibly some visual in the background? I heard some people say that there was some Greek reference, which would point to Ulysses, but I really just don't know. Again, this wouldn't become clear until long after the fact.

So, those are my brief little theories. What do you think? Let me know in the comments what you think of my theories, as well as WHO you think the killer is! Hope you enjoyed this!