UE4 geometry box light leakage

I’m actually new to unreal engine and i started building a modular house with geometry box so after i finished with the building i converted it to static mesh and i later found it out that they are some light leakage in almost all joint edges in the house! so is there any method to remove the light leakages from the building? because it looks irritating. Thanks!

Are the moderators still alive?? wow up to two days now still not yet approved!