Kaida, i think it could be as simple as the
juice being too thick or too much sugar content. I'm using the same exact setup. Evic with Aerotank, obviously 2 coil kanger head. I am using an Ejuice, which is malaysian, it is dark red, very sweet and thick. I finish my coil about the same time as you, 2-3 days. I tried 3.5volts up to 5 volts. Its all the same. The coil pretty much lasted 1 day, after that it was just inconsistent
vaping.
So i decided to change
juice. Im using some local mix, which doesnt use sweetener/sugar, its clearer in color, and not as thick. Now my coil is lasting much longer.
Try different juice first, if youre still facing the same problem, then try rebuilding your kanger coils.