"Entarten" is not a verb that can be used to describe the change of "Gesundheit", and it is not a valid translation of "to degenerate".
Valid translations for "to degenerate" are:
- degenerieren
Unsere westliche Gesellschaft ist zu einer Raff-Gesellschaft degeneriert.
- verkommen
Durch deinen Lebenswandel bist du gegenüber früher regelrecht verkommen.
More translations can be found on leo.dict.org.
"Entarten" means to become something from a worse kind, class or species (Engl. kind, species = Germ. Art).
Verbs that can describe a change of healthiness are:
Fatimas Gesundheit hat sich verbessert.
Fatima's health has improved.
Fatimas Gesundheit hat sich verschlechtert.
Fatima's health has declined.
Her healthiness doesn't become something else. It just becomes worse without changing the fact that it still is healthiness.