You didn't mention how long you vape the one juice without switching. You're right, it could very well be the dreaded "vaper's tongue". I find when that happens to me and I want to continue to vape the same juice, brushing the tongue, drinking more water, and not vaping for a little while fixes the issue. If I want to vape right away, I just go sniff some coffee grounds (just inhale the aroma of the ground coffee, don't sniff it into your nose) and that also helps to "cleanse the palate."
Of course, PG is the flavor carrier so more PG in the juice might help. Likewise, with max VG, your wick might not be able to get sufficiently soaked with the juice before you vape again. If you want, you can put a couple or three or four drops of distilled water right into your tank to thin it out.