I would try vaping unflavored for a day or so to see if you have developed a sensitivity to certain flavorings. The scratchy throat and cough developed for me after about a year and a half of vaping, and switching from all kinds of flavors to a mild mint/menthol eliminated the problem for me. It was worse in the dry winter months in my case. Changing the PG/VG mix didn't help when I tried going 100%VG. Good luck sorting this out!