Fenix 5 battery drain. Barely lasting workout and charging every other day

Does anyone have any advice or idea on how to fix my Garmin battery drain.

I get maybe 2 days with a full charge 

Even this morning it dropped 5% in the space of 1 hour.

If I'm working out,I have to charge it over night so it's full in the morning for the workout.

Started happening not long after a Spartan race 

Thanks 

Chris