What is happening to these normals?

I have some marching cubes with complicated formulas generating them, everything is 100% good except some of the shadows, and I don't understand why, for example, a single triangle can go through 270 degrees of shadows even when the triangle's corner normals are only 90 degrees difference.

here is a code for highlighting normals in scene view also for reference

 #pragma strict
 
 function Update () {
  
     var mesh : Mesh = GetComponent(MeshFilter).mesh;
     var vertices : Vector3[]  = mesh.vertices;
     var normals : Vector3[]  = mesh.normals;
 
     for (var i = 0 ; i < vertices.length; i++){//change all the UVs say they face flat on one axis
     
     vertices[i] =  transform.TransformPoint(vertices[i] );
     
          Debug.DrawLine (vertices[i], vertices[i] + (normals[i] * 0.1), Color.yellow);
 }
     
 }