Child Passport application Supporting Documents

[Mertex]

Hi everyone,
I recently applied for British passports for myself and my children. For my own application, after the passport status changed to “printed”, I received an email from Royal Mail with a tracking number. The passport and all my supporting documents arrived the following day, in separate packaging.
For my two children, their passports also changed to “printed”. However, unlike my application, I never received a Royal Mail tracking email for either of their applications. The children's passports arrived two days after the “printed” notification, but their supporting documents have not arrived yet. I paid an additional £5 for each application for the supporting documents to be returned by tracked delivery.
Has anyone experienced this before? Is it normal for the supporting documents to arrive several days after the passport, and is it normal not to receive a Royal Mail tracking email?