1965 Canada Silver Planchets (25c & Dollar Tested), Undocumented Planchet Weight Reduction?

I have had the great priviledge to find 5 x 25 cents from 1965, that are all BU, while coin roll hunting. They are all stunners brilliant coins as we rarely see today. I suspect they were just pulled right off a 1965 Mint roll, and mixed up with other coins...
I weigh each of them, and they all weigh between 5.78g and 5.80g. Nothing alarming since it should weigh 5.83g. However, I have some well-worn older silver coins, like a 1964 that weighs 5.91g and a 1959 with even more wear that weighs 5.84g. The reeds on both of the older ones show wear, whereas all 5 x 1965 are sharp new coins. I also bought a 1965 Silver Dollar from someone, that looks AU with sharp reeds and nearly all Mint lustre, that weigh 23.18g, but my 1936 and 1937 dollars that have more wear (not extreme, though) easily weigh 23.37g and 23.39g.
Any theory or thoughts on something?
Luc