Yes, the cleansing of the chemical crap from smoking can do that too.
PG is an irritant and hygroscopic humectant.
I'm curious to know if you have any sensitivity to artificial sweeteners - for instance does diet pop give you headaches too? I was getting severe headaches from a couple of juices I bought and I still suspect that was the culprit. I've found most don't use artificial sweeteners, but there are a few. I would suggest trying a different kind of juice, one you know is sweetened with Stevia or some natural sweetener.
Stevia is not recommended for vaping--per our resident chemist and DIY-er Kurt:
http://www.e-cigarette-forum.com/forum/diy-e-liquid/302964-flavor-spoilage-help.html#post6355337
Sucralose and ethyl maltol are considered safe for vaping.
Water.
Not juice; water.
How to know if you are well hydrated? When you go to the toilet and it comes out looking like water, then you're well hydrated.
If it's yellow, then you could use some water.