Two of the dead chicks were recovered by the Peregrine Falcons in Worcester team and sent to a laboratory for analysis.
The post-mortems showed the birds’ cause of death was down to ingesting poison.
Chris Dobbs, the cathedral’s biodiversity adviser said the results would be shared with the wildlife unit at West Mercia Police as well as the British Trust for Ornithology.
Because the nest had been under the microscope, “you see the good and the bad,” said Mr Dobbs, reflecting on the deaths of the chicks.
“It’s not a good thing to happen, but it does happen, so hopefully it won’t again, and we’ll have a nice normal year next time.”