Aha. Yes, I think that's the key entry to the theory. In fact, I wouldn't be surprised if Penelope's entry and Susan's entry have nothing to do with the actual food. Or Sally Anne's for that matter, but since she's a half-blood and it would make an interesting pattern, it's possible that she really meant it about lunch being off and wasn't using it as an excuse for why she was acting unsettled in the wake of Carrow's use of cruciatus. Or maybe she was sort of using it as an excuse, but it also happened to be partly true?

Anyway, it could still be a coincidence, but it's something to keep an eye on.