Bike fit will change for a myriad of reasons.
Maybe a tune-up fit is called for.
BTW is 37 seconds really a significant change?
Ambient temp can change my same bike, same route times by 30% or more.
And that's without considering headwind, or the fact I seem to faster in the mornings.
Which is faster a RED bike or a BLUE bike....... It depends on which one you think is faster!
Barry
BTW: it's a trick question... I know YELLOW bikes are faster!