@StoneRyno, no way to edit specific age within a life stage that I'm aware of. Even MCCC only allows you to move them to the start or the end of a stage. What I do when I'm in the position you are is freeze their age with MCCC until they are synced to what I want them to be at, then I unfreeze their aging.
Without using mods that let you freeze aging for just a specific sim, I've no idea how you can fix it short of timing a potion of youth to do it. Like if they age up 7 days earlier than you want, wait until 7 days after they age up, and use the potion of youth to put them back to the start of that new stage.