When my Hangsens change taste it's normally an indicator to me to change my cotton wick and clean my coil.
I always start all my juice tests with a cleaned and rebuilt topper, so that's not it, plus, I was only into my 3rd tank full using my Corolla 1.5 (3ml tank) when my flavor went flat. I'm thinking that like danny said, it's my ECX Nic doing it, I bet if I was using NN or one of the others that are cleaner, I might not have this problem, but I do like the TH of the ECX.
Looks like my INW Chocolate is due in on Saturday sometime, so will get to work on my Highway then.