Filling your mega evolution dex

Hi! I have 52/55 mega stones registered and all of them have akready been obtained through exchanging mega shards or buying them.

Also i already finished base game (savior of lumiose title).

Quasartico offers me no new options, which 3 could i possibly be missing?

How can people obtain shiny charm without the remaining 3 which i SUPPOSE belong to greninja, delphox and chesnaught and therefore require to participate in a yet to be opened ranked season.

Could someone please help me out? I feel lost and have no idea how to proceed.