I tried to delete them from Ancestry but can't because they were created from an FTM source template. It's a PITA but not the end of the world.
It means that when I want to change the citation detail I have to create a new citation, link it to the proper people and facts, delete the old one and then sync. I don't think it's worth the extra work.
Unlinking the trees, deleting the member tree on Ancestry, and then creating a new tree from FTM will fix it but that seems a bit drastic for this.
And, like you, I'm continually revisiting the citations and changing them to be better than what I had.