I made this recipe about 10 days ago, that 1/8" cut is a bear, I've been meaning to post on it. How did that go for your make? I ended up closer to 1/4" and upped the cook time a little to account for it.
What is your room temp where the mold is? My house gets cold overnight so i leave the sous vide for the make and put the press over the water bath on a sheet tray, it helps the cheese stay a little warmer so the culture can do its thing in bliss.
Recipe calls for 1/2t thermo b, 1 skewer tip thermo c for 4 gallons, and 1/16 propionic. So you were a little under on thermo and almost double on propionic.
For your substitution of thermo b/c, the book talks about these on page 275. The difference is thermo b contains lactobacillus delbruekii ssp. Bulgaricus, and c contains lactobacillus helveticus. Should be fine for interchange, honestly I am not sure why thermo B is called for in that recipe, C seems more in the style. What I am trying to say (longwindedly) is I don't think this was a bad substitution and shouldn't have caused your problem.
For my make it took over 24 hours to hit the final pH. I wonder if you are seeing a rebound from calcium coming out of solution. I would flip it and give it the remaining 12 hours before you start to get very concerned about it, it may still come around if your room temps are high enough.