Since updating to 4.2, destructible meshes have very low resolution texture quality. This is most apparent in the normal maps - In fact, it almost looks as if there is no normal map at all.
I have both destructible and non destructible meshes of the same model used in my map, and it is very obvious.
Have you tried re-compiling the shader? I was having some issues on skeletal meshes that seemed to be fixed by resaving the texture and recompiling the material.
I’ve submitted a fix for this in master (and should filter through to 4.5 release). You’ll have to re-generate your destructible meshes to ensure the normals are corrected. Sorry for the inconvenience!