I bought a queen before 3 weeks. I started nuc with three frames from my hive and introduced the queen.
Last weekend I opened the nuc and I found the queen for the first time. But that was not the queen I bye. I opened my hive and I found a plenty of queen cells. I obviously transferred the queen from my hive to new nuc.
And what did I do? I have been afraid of swarming and I transferred one frame with queen cells in new nuc.
Now I have two hives with two deep and two nuc. I hope that they will develop new queens?
I assume you mean you did all of this three weeks ago? If so, you should have a new virgin queen in the old hive by now and she should be laying within a week.
The break in the brood cycle might help with the Varroa mites.
I started first nuc before three week and secend befor three days.
I have done that too, I put the marked queen that I bought in the nuc that I thought was queenless, and as soon as she got out of the cage I never saw her anymore, and I couldn't find her body either. i couldnt find anyother queen either but I was smoking them so she might have been hiding, they have a queen now and are growing well
It seems to me we have quite similar experiences.
I will try without smoking this weekend. Good luck.