Deterioration
Degradation
noun, verbal noun
れっか
悪化 （あっか） Deterioration, Getting Worse
劣化 （れっか） Deterioration, Degradation
衰退 （すいたい） Decline, Decay
劣悪 （れつあく） Inferiority, Coarseness
Deterioration 劣化 is when inferiority 劣 creeps in due to a change 化 over time.
It's no longer lecker れっか (delicious in German) due to Deterioration.