I could try installing the newest armory software but I don't want to redownload the whole blockchain again. Is it possible to update armory separately? Is that what I should do here? I am a bit worried.
Help -> Rescan Databases
Restart Armory and Bitcoin Core (if you run it separatley), then let it scan and try again.
If it doesn't work, then try Help -> Rebuild & Rescan Databases. Will take a few hours, but it should definitely be resolved after that. You shouldn't ever have to redownload the blockchain unless there's reason to believe that it somehow got corrupt, but that's unlikely here (Armory is seeing a different history than Core, so it's probably Armory's DB that is out of whack)