iPhone apps

This happens because of a feature called offload unused apps. You can disable in settings under iTunes and App Store. Since this feature was already enabled, apps that you didn't use for a while were deleted to save space, this is indicated by a cloud icon next to the app name. You won't be able to reinstall these apps until you clear your storage but to prevent this from happening again just disable the setting under iTunes and App Store in settings. Hope this helped.

That means they have been offloaded, because the iPhone was low on storage space.

Delete content from the iPhone to make room for the Apps so they can be re-installed.

See here: How to check the storage on your iPhone, iPad, and iPod touch - Apple Support