so i've got two NPro RN4081 batts and a Tasty Vapor branded 510. i've got some tasty vapor cherry cola and rootbeer flavors, 54mg nic juice and some stevia extract...i did a 50/50 mix of flavoring and nic juice (1/2ml each) along with 5 drops of stevia...and there's like NO vapor at all. i've puffed and puffed with no good results. what'd i do wrong?