i guess you have to do more detective work!
the engine uses a lot of fuel while warming up so in colder/ winter weather consumption goes up perhaps 10%perhaps more.


what tires did you put on at the service (they can affect fuel consumption).
the CO setting might have been changed which can also contribute.
did you put in an different engine oil (Ihave experienced about 10% improved fuel consumption by using premium synthetic)
71 is very good but not surprising if your riding style is gently and you don't spend much time in traffic jams and at red traffic lights