Well, I've not used 700x, but I would venture a guess that it's got a similar physical build as 800x -- and that means it probably SUCKS when metered from a mechanical powder measure.
What most likely happened isn't that anything in particular happened over night... just that you were lucky for 6 shots and not-as-lucky for the other 6 shots.
Metering powders like that is a hit/miss proposition, and frankly, it's not a great idea if you are near squibs or near max.
Pick a different powder or get in the habit of weighing each charge if you want more confidence in what you are building. That's one of the reasons that you won't find a lot of folks discussing all their plans and experience with 700x!
