Okay, time to take it into stages. Already talked to a health professional, we narrow it down to one of the 4 ingredients and a step down of sort on others.
1) Vape on a unflavored nic liquid of your normal ratio, stated 30pg/70vg start there at your nic level, still having problems, go to step 2
2) Vape on an unflavored 100% VG liquid of your nic level, still having problem, go to step 3
3) Vape on an unflavored at a higher PG ratio, 70pg/30vg or thinner, if throat hit is to harsh, lower your watts down, still having problems
4) Vape on an unflavored, no nic liquid
Reactions are caused by one of those 4 base variables from the most common to the least common, flavorings (which are generally in PG), the PG itself, then the VG itself, then last the nic itself, once the culprit is eliminated you can most likely add flavoring again. Right now I am leaning toward the Menthol flavoring is tearing you up, that or if it from a new vendor of liquid if you do not DIY or a new flavoring vendor if you do DIY it the vendor's bases and flavorings giving you issues. Just my 2 cents and good luck.