The way most tanks work, at least those with the
juice tank on top, is that the tank only has holes at the bottom for the juice to flow and as the juice starts to flow out of the tank the replacement air can only come in through the juice holes at the bottom. The tank essentially has a vacuum in it thus preventing the juice from flowing freely out the juice holes. Wicking is usually also part of the equation as it slows the ability of the juice to flow out the holes such that between the vacuum in the tank and the wick blocking the holes the juice is only allowed to flow slowly and only flows at all because of the wicking effect of the wick material. It is sort of like a balancing act.
If the tank can't hold the vacuum or the wicking is not correct then the balancing act dosen't work and the atty leaks. So begin as daviedog suggests and ensure there are o rings for every joint/connection in your tank. Any place it screws together there should be an o ring. In fact if you have replacements then just replace the orings just be very careful removing and replacing them that they are not damaged by the sharp threads. You can cover the threads with some tinfoil or plastic wrap while you slip the o ring over them.
If that dosen't stop the leaking then look to your wicking. Check out the Youtube guru's and try to do what they do for wicking that particular atty. Watch 2 or more do it and get a consensus of what works best, they don't always agree with each other's techniques.