On the top are bits of solidified batter, as they crumbled out of the beakers (post #17). It is obvious that 1. the vanilla FO really discolours, and 2. the ZCS really works!
BUT still not the slightest trace of all this in the actual bars.
The main difference between the two is that I kept the bars at regular room temperature, but the beakers were placed on the radiator, i. e. are much more thoroughly dried (see also the more intense yellow).
I have three of the tabs. What I will do now is: 1. keep one as-is, curing at normal rate; 2. put one onto the radiator too, so that it gets an extra dose of warm, dry air; 3. do an “emergency CPOP” to the third one, i. e. put on a heating pad at 60°C for several hours.