Yeah, I'm definitely not using a diffuser. After some additional observation, I do think this is a case of air bubbles getting smashed into micro bubbles and passing right though the reactor. Surprising that it can appear as small as diffused CO2 mist but it's the most reasonable explanation. Made some adjustments to the skimmer and wasn't as noticeable today.
It certainly seems to fit the evidence. I'm glad you seem to have improved things.