Think I got my cloudy Lemon Cake mix figured out.
I made some this morning with just PG and LC. Clear as glass once the bubbles went away. Then I added some VG. It was still clear. Then I added some more LC and it turned cloudy. I did that to test out the theory @JCinFLA posted about adding the VG last. Looks like that is the explanation for the cloudiness.
Still not sure why my blueberry LC wasn't cloudy. I normally put the base in the bottle first then add the flavors. But maybe I did it the other way round that time. Maybe the blueberry flavoring has enough PG in it to stabilize the lemon. It doesn't bother me any more though now I know what causes the cloudiness. I was worried I had a bad bottle of flavoring or a dodgy batch of base. Maybe I'll try some more small bottles. Put the LC in the bottle first and add base. Or make an extra bottle of base with just PG and nic for making recipes with LC. Then I can mix the base and flavorings and add the VG on top.
When I started mixing, I remember Bill’s magic vapor telling me to always add flavors first and nic last. It’s become such a habit that I don’t even think about it now.