It may not be the juice or the hardware, but try another juice as a test for sure. This time of year my allergies really ramp up and all my juice tastes weak. I had my buddy try, that doesnt vape or smoke, and he says it tastes the same as it did before. I dont have any vaping friends, so whenever i get a new flavor I have him try it...he is happy to test even though he doesnt smoke. Ive also noticed my sense of smell has diminished quite a bit since my allergies kicked in.
On a positive note though, since I started vaping I rarely get allergy symptoms now, where when I was smoking my head and nose was constantly stuffed up.