Earning less GST day after day?

STEPNSTEPN
$1.35
‑10.66%
self.StepN1m ago
So I have upgraded my common jogger up to level 8, and for I have kept it for like 4 days on level 8. But I started to notice my GST total earnings decreased by around 0.20 day by day. Has anyone experienced something like this before? Or is it just coincidence? Edit: I do daily repairations