Transplantation day! They are now wider than their little 200ml pots, so I moved them to 1.5 gallons. I also supported the couple with some chopsticks, but they recovered in no time.
Also, this is the week I had the first leaf problem. Further investigation showed it most likely was overwatering.
The soil mix was a ProMix HP soil with 25% Worm Castings and the recommended dosage of a Gaia Green All Purpose. Tbh, I don't remember the exact measures.