One vertex darker with lighting

OpenGL OpenGL: Basic Coding
1

Hi. It’s just me with another lighting problem.
As you can see in the screenshot, my map is made up of a lot of small cubes and one vertex looks darker. Does this look like the normals aren’t calculating correctly?

Thanks,
Adam

2

i can’t see cuz my browser dont allow images. can you plez describe it to me?

3

Depending on what side you look at the cubes from, one corner is darker. Without lighting, it’s obviously fine.

4

It points most likely to wrongly defined normals.