Sudden death in chicks.

Eight weeks a go I obtained 7 fertile banty eggs or 'nain' as they are called here in France.

Successfully hatched 6 of them and they lived in my small ark for 5 weeks. Letting them out into the main run with the 6 other 'poules ' every day. The big chucks live in a spacious 'Chateau du Poules' and are all laying well.

As the chicks grew I noticed that 'mum' was being 'hen pecked' by the others.
Now 5 weeks old and becoming more and more independent I decided to put them back into the main residence at night. I had closed the door on the arc.

I went out last night at dusk and mum wasjust leading all the chicks into the chateau. They were all snug in one nesting box. Everyone was happy the 'girls' were all on their perches quite content and drifting off to sleep.

Thismorning at about 6.30 I heard the usual chicken chatter and thought Oh the girls are up. My husband went outside to do a few chores, squat the dog, feed the cats, fill the pool. bring me tea and feed the girls. First one up does this while the kettle boils.

Got bad news he says. We've lost a chick? I say.  No, all of them. He replied.

I went down to have a look. Expecting blood and gore. Nothing. Not a mark on them. Two still in the nest box, one in the box next door and two on the floor. One missing. The adults were a bit subduded but didn't seem particulary stressed. Mum  looking  a bit confused. I haven't got a clue. Was it fright, stoat, something they ate?
I am so disappointed and upset. This is the first brood I have hatched, I don't like to keep a cockerel as I sell the eggs to local B&B's and gites and I never did like cracking fertile ones.

Does any body have any thoughts as to the cause. I still have my 4 original 'old girl' I bought 4 years ago and they are still doing fine.


Cactus0033