I am injured and unable to run anymore but the only piece of advice is do some speed training. My neighbor and I did like 5 mile speed days every other week. It made a world of difference...
Suggested speed workouts:
1) Run two sets of 6 x 400 at 5K pace; jog a 200 for recovery. Take 4 minutes recovery between sets.
2) Run 6-8 x 800 at 10K pace; jog a 200 for recovery.
3) Mile Repeats: 4 x 1 mile at 30 to 45 seconds faster than your goal race pace. Take 3 minutes recovery between mile repeats. Do these on the road, not the track.
Suggested guidelines for speed work:
1) For mile repeats, use 30 to 45 seconds per mile faster than your goal marathon race pace. For track intervals less than one mile, try a pace of 60 to 75 seconds per mile faster than your goal marathon race pace.
2) Use a consistent pace. No more than a 5-second variance in mile repeats or intervals.
3) Track workouts should be no longer than 5 total miles. For longer workouts, use the road.
4) Do mile repeats or 800s during or after higher mileage weeks
5) Do the 400s workout following shorter or cut back mileage weeks