Actually, no. The only thing I can think of is either a big temperature change (and then the wine formed a vacuum), or a big drop in barometric pressure or something.
You have the airlocks filled right? So air isn't really getting sucked in? I would probably remove the airlocks, clean and sanitize, take a s.g. (and a little taste) and put the airlocks back on.
If it's got sediment on the bottom, I would go ahead and rack and sulfite just to be sure it's protected.
Lorena