Meltryllis

Currently trying to edit the Lake Trio and a Golurk I caught to be shiny, and I'm unsure as to why they're being marked illegal when these encounters can be shiny. Am I unable to change Pokemon I've caught through Max Adventures into shiny, and why?

Yeah, fair. Just double checking before I do something stupid. Thanks a bunch!

I'm looking to transfer my shiny Gardevoir and Registeel back into Sword since I started a new save, but they have...really stupid nicknames. I'm wondering if I can change their nickname with PKHeX and not get any warnings. (Also, mildly related, does anyone know why nicknaming a shiny Diancie doesn't get flagged?)