You noticed a change that quickly? That's pretty significant, and whilst im no professional in either the health or vape field i'd presume it was related to the juice(s) you've been vaping. I'm not sure what your access to eliquids is like, but maybe it's worth trying one or two new suppliers and preferencing VG or PG heavier liquid, whatever is the inverse of how your current juice is balanced(If you're vaping VG heavy, try juice heavier on PG, or inversely).
EDIT: Sorry yes you did mention this earlier, maybe try PG heavier liquid and see if things change(or just change the supplier - maybe something your particular supplier uses in their juices doesn't agree with you).