I run marathons.

A generally accepted training methodology involves slow runs being the bulk of your weekly mileage. Most plans involve three key workouts. A speed day, a threshold day, and a long run day. The first two are faster efforts while the long run can be uptempo if you want but also slowed to ensure adaptation is occurring over the build.

Looking at OP’s cumulative weekly km’s, I feel they’re not exactly running a lot during the week relatively to a typical marathon plan. But imagine these three sessions take up 20k in a week, the remaining 40km being slower would reduce the average pace overall.