Microphone

if it works for some stuff and not these specific apps.. and they have access to the microphone.. Maybe try turning off your phone and back on. Otherwise it's more than likely an issue with their app.

How to contact an app developer - Apple Support

here is a support article from Apple. Basically try recording a voice memo, then play it back. If it works, then they point to the app developer

If the microphones on your iPhone aren't working - Apple Support

Hi rbia273,

I have exactly the same issue on iPhone 12. Is your issue resolved and if yes how please?

The microphone is working on regular calls (phone on ear), iMessage and Camera videos, and it is not on speaker mode calls, whatsapp, Messenger, Siri and Voice Memos.

Thank tou for your help.

Did you get it fixed ? What was the problem I just got an iPhone 12 like a week ago and I’m having the same issues microphone doesn’t work on any other apps just on iMessage but you can barely hear anything

If you check Settings > Privacy > Microphone, do these apps have the switch turned on?