How do I prevent YouTube, WhatsApp, and Snapchat access during downtime on my daughter's iPhone?

I set up downtime on my daughter's phone. But once downtime comes on she can still access YouTube WhattsApp and Snapchat.. I have tried everything, from adding App limits for each of these apps individually yet somehow they seem to be oblivious to the workarounds. It’s completely unacceptable and I need a solution asap.

[Re-Titled by Moderator]