Here's a great way to fix 'em! 'Don't know why in the world we didn't think to mention this before, because "fixing a broken juice" is one of THE best ways to come up with an unexpected winner (and we always learn a lot that we can apply to our future mixing).
Take the a sour one, and dilute it with equal parts unflavored nic base (nic base = your standard mix of pg, vg and nic to create your nic level), mix/shake it thoroughly, give it a little time in a hot water bath, and then test-vape it. "Equal parts" should be a big enough of dilution to 'water down' the intense sourness, but if not you can dilute it further (or you can start by diluting it with less unflavored).
Then start fixing the new dilution...do that by adding small amounts of whatever sweet flavors you've got that seem like they might work with the mix. Be sure to keep good notes, because you'll virtually always come up with a blend you'll want to make again.
Good luck!