Mesh Triangles Faces are visible in Game but not in Mesh Editor

Hi, I have an FBX exported from Blender (i’m a noob in all things) that looks fine in Blender, and fine in the UE4 static mesh editor, but in the game as played in the editor (PIE) the mesh triangles are visible, and some of the faces look very obvious. I don’t know what is causing it or how to fix it. Attached is a pic of the game and mesh editor so you can see what I mean.

Thanks for any help.