The amendments have always been sent from the US (Denver). The Canberra office, and before that, Dandenong, only kept the records and provided one-off amendments.
However, with that said I did notice the other day that the postage on the envelope was Deutscher post, or something similar. Jeppesen these days is a Boeing company and has been for a number of years and they may be altering their distribution centres to suit corporate reasons.
Perhaps a reason for the delay is the decidedly ordinary weather they have been having in both the US and Europe.