Mystery Peleton sync

I have a weird situation that I would love some help with. I had a whoop that I was using as a heart rate monitor with my peloton tread. I then decided to give my whoop to my son, so I deleted the whoop from the peloton tread. However, now whenever I go for a run, my son still sees the run show up in his whoop app. How can I get the tread to stop syncing with the whoop app? Thanks!