looking at the graphs which you have linked, my results with the cyan ink begin to make sense, as the black lights i use emit light at 370nm and looking at the graph K is the best blocker followed by Cyan and very closely behind is the yellow.
I think inorder to my process goinin the right direction, I may have to start all over again, perhaps just with the black inks first and add the other inks as neccessary, as I do believe that that will give the best separation in the greys.