So we have the bread and butter basic schedule - 1 Speed work day, 1 tempo day, 1 long run and lots of mileage. Has there been anything you have done that's made you faster BESIDES those things after a long plateau (over 6 months). I'm specifying this because runners tend to have a few bad races, add something in and then attribute their success to that when the reality is they just raced poorly and their training was working.
Some examples to start:
Strides, Weightlifting, changing the order of runs, doubles, sprint development drills, hills, duration of runs, more tempo, more speed work, easy/hard ratio changes