Sensitivities and etc can certainly arise any time. The problem with closed pod units is you aren't even going to know exactly what you HAVE inside them (and I'm not just talking PG, VG and flavors, there may be other items added that, if proprietary, it's going to make it hard to know if there is something else causing you irritation and etc.
If you decide to do some elimination experiments, I'd suggest maybe some sample packs from vendors, (small ones) of various ratios of VG/PG and flavors. Or, you could buy small amounts of PG, and VG, and experiment in your vape to see if one is causing a problem or the other, then add in flavors. If you don't want to DIY completely, well, at least you might be able to get a handle on if Pg or Vg is a "main offender." That may help you moving forward.
It's not unusually for a person quitting cigarettes (if you are) to feel odd, or have detox symptoms, I'd highly encourage you to read the list of quitting symptoms and I'm so glad I did. I have thyroid issues, and had no idea that vaping actually impacts thyroid function in a different way than cigarettes, for example.
Please read up, decide on a plan of attack, and if you continue to have trouble, see a doc. Mine (he is also a vaper) really helped me figure out my PG sensitivity,. Also, I can't vape vanillas, they make me hoarse. No idea why, and I LIKE vanilla, but after trying 3 different manufacturers, I was like, well, forget it. Etc.
Best of luck,
Anna