Ohh I used to know a family who this kept happening to. Lots of hamsters bought in quick succession, mostly young Syrians, who kept dying "mysteriously" a few weeks after being brought home. The family blamed Pets At Home for selling faulty animals and were very surprised when I said that we had bought a fair few hammies from the same branch and they had all lived to a ripe old age!
I don't think the family in this case were being deliberately neglectful, just a bit clueless - I later found out that they had loud dogs in the house as well as young children, and were letting their toddler (man)handle the hamsters from Day 1. They had no idea that hamsters can literally die from stress. Their cage was also very small with only tiny house, a food bowl and a broken wheel so the poor hamsters had nowhere to hide from all the noise and grabby toddler hands.
Maybe try and find out if there's a similar environmental issue in this case? It is a tricky situation though - hard to bring up without people getting overly defensive!