Pretty normal for bottom air flow RTAs I'm afraid. Generally there will be a light build up of juice on top of the mod just by the air inlets on the bottom of the RTA that you should wipe away periodically. When you fill the opening the top cap releases the pressure inside the tank and a little liquid can get pas the wicks, find its way into the bottom of the tank and dribble out of the air inlet and on to the top of the mod - closing the air inlet helps reduce this.
When you fill it - first close off the airflow, take the top off your juice bottle so it is ready to fill the tank, open tank cap - fill immediately and close as soon as it is filled. Take a few hits immediately after filling to restore the pressure in the tank. Never open it, get distracted and fill whenever or whatever juice is left in the tank WILL leak out.
Bottom airflow RTAs are always going to be slightly wetter/leakier than top airflow versions, but generally they give better flavour so are worth the hassle - but wiping off the mist/pooling on top of the tank is an issue. Generally I remove the tank and dry the mod at every fill, generally I wouldn't worry unless it is excessive - if it is you need to wick a little tighter..