Separator line after Instantiate random objects

Hi everyone …
I used Instantiate to create random objects … each object represents room in my game …
there is a black line or something like separator between each two room …
i don’t know if it related to rendering or what !
can anyone help for that !
thanks in advance alt text

it seems like the two objects (rooms?) are overlapping each other…
or you have textures error (texture bleeding …) like this: