Find a strong healthy colony that you can steal a few frames from.
Set an empty nuc box in a location that you can tolerate. Remember, your last queen from the 15 may be released in this nuc!
Take an empty frame with no foundation and tape the queen cages to the underside of the top bar 3/8" apart with the candy side up.
Place the frame with the queens in the middle of the empty nuc.
Locate the queen in the strong colony and set that frame aside. YOU MUST FIND THE QUEEN. You cannot gamble on her getting into the nuc!
With the queen from the strong hive set aside, pull one frame of sealed brood with attendant bees and install it in the nuc next to the frame with the queens.
Pull a frame of mixed eggs and larvea and install it on the other side of the frame with the queens.
You now have 3 frames in the nuc. Now add two frames of feed to the nuc.
Now, gently pull frames from the strong hive from the region of the brood nest and shake all of the bees into the nuc.
Continue until the nuc is overflowing.
All of the field bees will return to the parent colony but you should have enough nurse bees( that are not oriented) to cover the brood.
As long as you have brood in the nuc they will take care of the queens. That means that you may have to pull a frame in a week and re-place it with brood again if you don't use up the queens.
You can store queens for weeks in this manner.
I have exactly ONE less dead-out than you.
That makes my opinion beyond dispute!