I had another peek into hives B, C and D today. I found brood in all 3 hives. This is not the same as the brood which I moved. It's new brood on the new comb. The brood in D must have been there last time I looked.
The bees are building fresh comb. Over time they line brood cells with propolis, causing it to darken. When it's fresh, the comb is very white and gives almost no contrast to the larvae. That might be why I missed it.
Brood should mean an active Queen and a hive ready to build up it's strength. That's welcome news.