Agree with most comments so far. 6 mg. is way too high for me. Lowering the nic first appeals to me. Might give 1 mg. a try. You can always bump it up 1 mg. at a time. I would want to balance nic so that is satisfies at the lowest acceptable setting.
Might want to go through:
A list of symptoms when quitting tobacco and changing to an ecigarette
As everyone else has stated it definitely "sounds" like nic sick. Not sure what your normal nic level is or if you are testing these on a different device than your normal every day setup? But i drip 6mg all the time and often a bit higher (just made an 8mg last night). If i go up to 12 i can feel it and have to stop after 5 or 6 puffs.
Even if the bottle says 6mg you could try cutting it if you have any plain pg or vg, or a 0mg nic premixed juice. Most times i have heard people talking about bad PG\VG it has to do with taste. I have never really seen any comments where bad 0mg base made someone physically ill, not talking about personal preference or true PG sensitivity here. Finally was it pre-ordered in this strength? mixed to this strength by you?
I drip 3mg at high power and direct-lung-inhaling, and often need a couple hours pause and just the thought of nic or vaping makes me feel like vomit

I also don't do more than 6 draws at most before feeling "nicely-filled-up", and it's a fine point between that, and too much... As stated whats your usual strength and is it your regular equipment used? Mg's isn't really saying anything, as the way you vape, inhale and at which power level and equipment used is just as important if not more...
Agreed, I have had bad VG many times, but never got sick from it, but solely a taste issue..
thanks for all this feed back,
i usually vape 6 mg nic, except for my aroma ejuices which are 12 nic, and what i vape most often.
my last juice purchases i ordered everything in 12 nic and it was like a swift kick in the throat. literally left a lump feeling in my throat. and very scratchy feeling.
i did not feel any of this with the unflavored eliquid btw.
i bumped up to 12 nic as i've been vaping over 3 years and am still smoking. I find a juice i like and it never tastes as good a few days later. I've wasted lots of money on vaping and juices. I'm really trying to kick the smoking.
i have vaped this only in a little anyvape cerotank, with aspire bvc coils.. pretty simple set up.
i just checked and the voltage was just at 3.4 volts the coil is 2.0 ohms.
is it possible i don't have it high enough voltage??
the only other toppers i use are sophias and dripper pros.
none of which i vape over 4.0 volts.
Again, the taste was good. it tasted clear. no flavor really.
i vape mtl mostly, i don't inhale completely into my lungs usually. it's like a long draw, then a just pull it in to about the back of my throat and do a slow release.
I'm struggling in my long vape journey. And i'm really hoping that DIY solves my problems as i find most of these premade flavored juices to be really strong in flavor and unenjoyable for any length of time.
this is a big set back for me. So i really am trying to figure it out.
so far from the reading i've done and the advice here i gather,
i may not have shaken the 120ml jug well enough....
Could it be the low voltage not really heating the nic??
Most likely the pg/vg is not bad as it doesn't have a bad taste or odor.
I'm most likely not allergic to vg or pg as i've been vaping these ratios all along....