It looks like you extruded the top face, scaled it, extruded it again, and afterward didn´t UV Unwrap again. Blender only provides automated UVs for default meshes. So the cube is perfectly unwrapped, but any modifications to the cube, are not. That´s why your Texture is stretched because your UV for that area is literally 1px tall.
Perfectly Wrapped
Modifications are not automatically Wrapped
A quick fix in Blender for simple geometry like that: Smart Project the UVs
For more complex geo you really want to manually set your UVs but from my experience, in most cases where it is not thaaaaaat important to have perfect UVs, Smart Project is more than enough.