MissBeehavin, first off you need to determine what type of QCs they are building (as suggested by Rich0909).
At the risk of repeating myself ad nausem there is an excellent guide on QCs and what to do
here.
I understand it is their instinct but hoped they would have stuck with her a bit longer!
I think your assumption is that this is a supercedure, if as you say the queen is healthy and good, this would be unlikely.
Healthy bees make swarm cells this time of year in order to replace the current queen that will take off (swarm) with half(ish) the colony. This is the way the colony divides to make increase.
Killing good Queens (in my opnion) is not a good thing to do. You want to keep that queen (I think there was a thread on here recently about Queens being at their best in the second year, probably no conincidence as their second year is when they would take off and start building a colony from scratch in a new home).
If the colony has set itself on a trajectory where it wants to make increase and divide then you should be grateful for this. You should also give yourself a pat on the back that you've got them through the winter strong enough to be able to do this. You won't stop them swarming by removing the swarm cells. They'll only build more and more likely swarm early. So you may risk the colony swarming and not leaving behind a replacement queen.
As others have suggested (if indeed they are swarm cells) I would strongly consider making an AS or otherwise you risk loosing your queen. If you don't want it then you can always sell the nuc to a local beek.
Bobster
