So today we went out to re-fill the buckets of feed and to look for the brood and the as-yet-unsighted queens.
First we opened up the apiarium Valentinium. The feed bucket was empty, so Brenda refilled it with a half bucket of sugar water: she put in a quarter bucket of sugar, and then filled it with hot tap water to the half-bucket level. I pulled out frames and saw plenty of honey, but no capped cells that might contain brood, apart from a queen-cup (!?). And, yes, we finally spotted the queen! (She's the one with the white dot.)
We put in a fresh half-bucket, closed up, waited a bit, and then opened the Benedictium. We saw plenty of burr comb, including on the bucket, plenty of capped cells, brood, I hope, and the queen. We re-filled the feed bucket, emptied within the last week, with another half bucket of sugar water.