Effect of the marathon on our park run time

The graph below shows the noticeable impact of the marathon training on our 5 km park run times. 

For the first 6 months (blue background) our only training is touch rugby which gets us moderately faster (~30s over 6 months). The break (white background) is due to a busy period in the touch rugby calendar. Then the last 3 months (yellow background) coincides with the marathon training and results in the most significant pace increase (~60s over 3 months).