Combining meshes with correct tiling

I was facing a problem with the performance of my game when I was instantiating each block separately. Now, I've combined adjacent blocks in one block, then combined them all in one mesh.

My problem now is that the tiling of these blocks after combination has been distorted.

Maybe that's logical because these blocks now take the tiling of the shared mesh. But the scaling is different, so they are not supposed to have the same tiling.

How can I solve this problem please?