I've had to significantly increase my water intake since I started vaping a couple of years ago. If I get dehydrated, I develop very thick sinus and throat mucus that doesn't cause a traditional stuffiness/congestion feeling (i.e. I can breathe normally), but coats those respiratory areas and causes barely recognizable flavor components to linger as a scent or as a taste.
Teaberry juice (high or pure PG, so it's not the VG hanging around) gives me a strange floral plastic-y smell if I fail to keep up with my water intake, for instance. You might try drinking more water and perhaps some tea as well to see if if affects the sourness.
Good luck -- hope you find a solution!
Yes, this is definitely something I've noticed. Drink up!