Canada Post

Four Christmas cards out of 15+ sent out to family over three weeks ago were returned to our address today. The reason was, for all four of them, MOVED/Unknown/Wrong address by the Canada Post sticker on them. Even though all were addressed correctly, as I checked with family members via social media, names were correct as well as postal codes. Secondly, a little weird all four would show up back here on the exact same day in the mail.
Why?
I tried to make an on line complaint on the Canada Post website but I could not figure out how?
By the looks of the envelopes they never even made it out of Petawawa/Pembroke, Ontario area as they were not stamped and dated as being processed by Post office, unless they do not do so anymore?
All these things are too coincidental to make this totally seem fishy?