iPhone 12 mini overheating when using some (not demanding) apps

Hello there! I am having a somewhat strange problem with my new iPhone 12 mini. The iPhone is overheating when using specific apps. I have observed it with Tapatalk (forum app) and News 247 (news app from Greece). When using other, far more demanding apps (e.g. 3D games, YouTube, Spotify) there's no overheating. In order to be as objective as possible I have closed all apps running in the background.

Any explanation? Can it be considered "normal"?