How much PG vs. VG?  Sometimes that can make a difference, although since you raised your nic level, I might suspect that.  Lowering PG (maybe, might) compensate for that though?  It's a though anyway.
Nic salts have almost no throat hit, so if you are venturing into higher nicotine territory, a nic salt juice (or even just using your regular juices but bumping up nicotine a bit USING DIY nic salts might help. IDK. It could be the different flavorings, too.
Best of luck getting it sorted out. 
Anna