When you mean caffeine crystals are you saying that it actually gives you a buzz??
Yep, it gives you a buzz

There's 50mg/ml caffeine in the DE concentrate, and 25mg/ml in the premix (likewise the Green Cow, but twice that in the Kola Kick and the soon-to-be-unleashed Red Bullet

) It's not a huge quantity, and it's unlikely to add more than the equivalent of a cup or two of coffee to your daily intake even if you vape it all day, but it's enough to give you a noticeable lift (it helps that it's absorbed straight into your blood stream, rather than having to slosh around in a stomachful of other stuff before it's absorbed.)
Yeah one of the flavs is Doppio Espresso and the other White Choc.
The white chocolate won't be caffeine, but it is a flavour that's only partially soluble in glycols, so it
louches like Absinthe in water, which will make it look cloudy (Lemon Meringue does this as well. Funnily enough absinthe doesn't louche in PG, but it does in VG or water.)
But don't worry, it's all volatile.
FFR the vanilla concentrates also can sometimes form crystals of vanillin in the bottle if they're exposed to low temperatures (it's a pretty much saturated solution in the Very Vanilla and Vanilla Ice,) but again, nothing to worry about (vanillin vaporizes at 285'C regardless.)
It's sometimes tricky formulating these things to cope with temperatures ranging from an unheated aircraft cargo hold at 30,000ft to the blazing heat of a metal mailbox in tropical climes, but rest assured even any solids you observe are volatile, and will redissolve with a bit of heat.
Ill try to see if I can remix it with PEG only. Do you use DV ?
I make it
I bought Cognac, White Choc and Doppio and so far not having any luck with the mixing flavours...and its not my taste buds cuz i got some premixed juice and their great. Do you have any advice or recipes u care to share?
If you want to recreate the premixed juice exactly, then 15% flavouring (for these and most flavourings, but not Diablo Loco or Menthol!) 10% AG/VG and the rest PG should make a juice that's indistinguishable from the premixed.
But I prefer all PEG-400 mostly (though it performs less well with part-used atties, so I tend to start them off with PEG, and finish them off with VG to max the lifespan. You can mix the 2 of course, if that's easier.)