Brighter border when lighting is applied on tiles

[iSamurai]

Hi,
When I apply point light to a tile map that consists of a tile which is pure color, each tile's border looks brighter.
I set the tile's shader to be tk2d/litBlendVertexColor, and the sprite collection's generate normals only.
Is there a solution to this?
Thanks

[unikronsoftware]

Screenshot, please? I dont think I understand the issue.