Communal nursing is always a little more problematic during the first 10 days, the babies are very fragile, the females often fight over them which can lead to severe injuries and death is it the case here? I would doubt it usually you will lose a few babies but not the majority, why is why I chose to keep female alone with their litter for at least the first 7 to 10 days, than I put the female together to raise their litters by than the babies are stronger already.

In your case there are various possibilities.

Since they were alive when they were born you can dismiss that possibility.

Babies might have die later on it is very possible, the mother could have failed to nurse them (new or bad mom) or no be able to nurse them (not producing enough milk).

The female might have killed the babies, that happens too it can be due to stress, presence of another female, lack of food, lack of water etc

You can give her another chance if this time I would recommend to keep her by herself to see how it goes with a litter and if something like that happens again I would retire her.