Very nice photos!

Agreed, something seems off with the Norton 4K. The edge should be getting straighter here than it was at 1K, not worse. That doesn't even look to be improving on the 1K stria, just same/same.

Your coticule is probably 8K equivalent or lower. Look at the Norton 8K, then look at the coticule. Only a very slight improvement, if an improvement at all. I don't know how many laps you did on the coti, but I wager not many yes?

You could probably cut the Naniwa 12K out, Get the 4K hone sorted out, then go from the Norton 8K to the coticule and come up with very similar results to what you're getting now. Such is my 2 cents, take it for what it's worth.