It looks as though the detail is completely missing within the exported version. I think lighting may be a key factor here. Maybe try and re-create the lighting from scratch? Maybe you could also re-import the textures and re-create a material instance? This video may also help you to increase your render quality Unreal Engine Tip 7 - Achieving Better Rendering Quality - YouTube.
Is your computer powerful enough to render out at the quality you want? I’m not sure what compromises the Unreal Engine makes to allow users to render with a lower end computer, but it could be a factor.