Eek! Such pretty succulents, and how rare too! Congrats on getting then to bloom! Seems like the monanthes was in better condition than expected!
Yes, all lithops that I'm aware of (although there could be exceptions) bloom in autumn, usually pretty late too. After their flowers fall, you'll stop watering them completely. That's when the splitting season begins. The roots go dormant, as the plant focuses on absorbing all the nutrients from the "old" skin, and redirecting them into the "new". This process takes time, and unfortunately it might worry you a bit. For some perspective, I've got two lithops that have yet to be done with splitting. They're close, but not yet done