The greatest likelihood is the bevel stage. If you are using the thumbnail test to assess the bevel it is rather difficult to distinguish between a nearly and fully set bevel.
The difference between the shaving quality off of a Naniwa Superstone 12k and a more expensive natural stone is going to be relatively subtle. If you get pulling and cannot get a good shave off of the 12k, then spending more money won't fix this.
Spending more time on the 1k probably will.