You could layer your Bump Map and Colour Channel with a tile grid. By the looks of it, your Colour Channel already has a Layer operation so you should just be able to add it on top. The bump map you will have to copy down the settings, add the Layer operation, reapply the previous filter, then add the grid. You could also add the tile grid to the Displacement Map to get more definition.
Assuming the warping of your lines is caused by the distort operation in the colour channel. You would just need to change the order of your layers so that is it not affected.
- add the marble map to the color channel
- in diffusion you add under texture a procedural map - tiles - mix mode normal
- settings in screen shots below ( like change all colors to white etc. )
- if you like bump on it do the same as in diffusion.