Hey there Skaarl,
Thanks for reaching out to Apple Support Communities. I understand you’re having issues with using cellular data on certain apps on your iPhone. I’ll be happy to help.
If cellular data is enabled for these apps in Settings > Cellular, turn the feature off, restart your iPhone, and turn it back on.
Restart your iPhone
See if this has any impact on the issue. You may also want to make sure the apps and your iPhone are up to date to further isolate this. These links can help you back up and update:
How to back up your iPhone, iPad, and iPod touch
Update your iPhone, iPad, or iPod touch
This link can help you update your apps:
Update apps or use automatic downloads
If that doesn’t work, delete one of the apps in question, restart, and install the app back onto your device ensuring the cellular settings are on.
View or change cellular settings on iPhone
Let me know if this helps.