There are several things that it could be, it's just most likely to be your wicking. It's a process of elimination.
But I'm pretty sure it's not the wicking tho since I even tried to use the premade wick that came with the tank
Remember doing the wrong thing multiple times doesn't necessarily make it not wrong.
"The content of the tank is a column of juice suspended above a wick, which acts as a conduit to the coil. The flow resistance of the wick material and the
negative pressure above the liquid at the top of the tank are the forces that prevent the juice from simply pouring out the bottom."
So if there is a sealing issue at the top of the tank, this will allow air to enter and equalize the slight negative pressure in the airspace above the juice. You will get leaks.
Check and possibly replace your o-rings.
If the wicks are not dense enough, or are not long enough to sufficiently cover the juice conduits at the bottom of the tank, you will get leaks.
Increase the wick density, slightly lengthen the wicks and ensure they are completely covering/sealing the juice flow holes at the bottom of the tank.