Random plant event: Euphorbia trigona 'Red'

I bought my E. trigona 'Red' two and a half years ago, a little before leaving the garden center job. It survived fine and was willing to grow for me, but it didn't produce any branches, on any of the five stems in the pot, for the first two years I had it. This seemed especially strange because the green version of the same plant was branching a lot. So this spring, I divided the five stems into