Failed queen cells after grafting

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I've turned my hand to grafting for the first time this year, having previously just used 'natural' queens, and one partial success using a cupkit.

I set up a queen-right colony as per the Ben Harden method (brood box about a QE with a frame of open brood and 2 frames of pollen and spacers) and added a frame with 20 grafted larvae, aiming for them to be as small as possible.

I checked 6 days later and had 12 of the 20 cups drawn out and capped - though quite a lot of the cells were shorter than I would have expected. Additionally there was a bit of lacing going on.

Coming to use them today (day 14) and while 3 or 4 of them seemed viable (larger cells, signs of movement when candled), the rest were all entombed in lacing, and weren't looking good. When I cut them open there were dead worker-sized pupae (though still 'fresh' looking) that didn't seem far on enough for 14 days (looked more like 11-12, with eye colour just appearing, going by this picture: https://ars.els-cdn.com/content/image/1-s2.0-S1226861514001423-gr1.jpg)

Now what confuses me is that most of these dead pupae had a ton of royal jelly still uneaten in the bottom of the cells, and the cell bar was absolutely covered in workers. the brood alongside was also all perfectly capped over, with no signs of neglect.

Does anyone have any idea why these larvae didn't reach full potential? It doesn't look like initial neglect or a lack of food, so I'm left wondering what else might have gone wrong later.

Bonus points if anyone can tell me how long a mini-nuc of workers can be kept queenless for (and if they should be closed up the whole time?) I have some natural queen cells due in a different colony, but not for another 7 or 8 days...

 

[B+.]

I've turned my hand to grafting for the first time this year, having previously just used 'natural' queens, and one partial success using a cupkit.

I set up a queen-right colony as per the Ben Harden method (brood box about a QE with a frame of open brood and 2 frames of pollen and spacers) and added a frame with 20 grafted larvae, aiming for them to be as small as possible.

I checked 6 days later and had 12 of the 20 cups drawn out and capped - though quite a lot of the cells were shorter than I would have expected. Additionally there was a bit of lacing going on.

Coming to use them today (day 14) and while 3 or 4 of them seemed viable (larger cells, signs of movement when candled), the rest were all entombed in lacing, and weren't looking good. When I cut them open there were dead worker-sized pupae (though still 'fresh' looking) that didn't seem far on enough for 14 days (looked more like 11-12, with eye colour just appearing, going by this picture: https://ars.els-cdn.com/content/image/1-s2.0-S1226861514001423-gr1.jpg)

Now what confuses me is that most of these dead pupae had a ton of royal jelly still uneaten in the bottom of the cells, and the cell bar was absolutely covered in workers. the brood alongside was also all perfectly capped over, with no signs of neglect.

Does anyone have any idea why these larvae didn't reach full potential? It doesn't look like initial neglect or a lack of food, so I'm left wondering what else might have gone wrong later.

Bonus points if anyone can tell me how long a mini-nuc of workers can be kept queenless for (and if they should be closed up the whole time?) I have some natural queen cells due in a different colony, but not for another 7 or 8 days...

It's possible that the larvae you grafted were older than you thought.
I really don't like larvae in the starter. They take a lot of food that you need your grafts to get.
I prefer to raise brood over a queen excluder for 9 days until it's sealed (then destroy any emergency cells). Then , use that to raise the larvae. They'll get ALL of the food they can produce and grow to make great queens.