There's also greater variation in pace as the race approaches. Probably due to the varying distances ran in the higher volume weeks. In September, there's 1 run that is below the 4:30 pace which is presumable a short run focused on pace vs the ~5:45 pace run in the same month which was likely a much longer run.

In the beginning (October) it seems that all runs are cluster around the ~4:40 pace, so they were likely more consistent in effort/distance and much shorter.