How do I rotate a mesh about its axis with three.js?

Three.js beginner here, I'm trying to create a 3d-ring like structure composed of separate meshes that I union together using CSG. I managed to place each of the separate meshes along a circle. How do I now rotate them so that the long side of each one is facing the center of the circle (I believe this is rotating about the object's y-axis)? The meshes are currently all facing the same direction, and what I have so far.

However, when I tried rotating one of them about the y-axis, it did not rotate inwards towards the circle as I expected. Instead, it rotated like this. It does not seem like it rotated from the center of the position it was previously at.

I tried the following code to get this result:

mesh.position.x = 0;
mesh.position.y = 0;
mesh.position.z = 0;
mesh.updateMatrixWorld( true );
// Also tried "mesh.rotation.y = ((2 * Math.PI) / 10) * k;" instead of the following line:
mesh.rotateY(((2 * Math.PI) / 10) * k);
mesh.position.x = 25 * Math.cos((2 * k * Math.PI) / 10);
mesh.position.y = 0;
mesh.position.z = 25 * Math.sin((2 * k * Math.PI) / 10);
mesh.updateMatrixWorld( true );

Thanks in advance! (Also side note, if anyone understands why some parts of the meshes are randomly becoming non-existent/transparent, would be super helpful).

EDIT: JSFiddle Link