Actually your focus upon what is important might have shifted a bit, which made your 5. kyu techniques look stiff. When we get better we get new points of interest in our practice, and we have to incorporate these new aspects in every technique. Your 5. kyu techniques might be very good compared to what a 5. kyu grading focuses on, but in your own eyes you see something missing.
That is one reason why specific techiques for a specific grading is not allways good. One should allways expand ones new knowledge to every technique ever praticed. Maybe that's one reason why there is ever longer time between gradings
You must accumulate more and more.
Is this making any sense at all ?