Roots Excelurator Gold formula getting mold growth.

I've been through two liters of the gold formulation so far and each time some sort of fuzzy mold started growing in the bottle that produced a most foul odor. I can't recall it ever happening before, is anyone else seeing this?

I still have a silver bottle from a year and a half ago and theres no sign of mold on it, and it sits in my garage that gets up to 100 in the summer and humidity is over 50%