Learn Farsi: آنها در خصوص بهداشت مورد توبیخ قرار گرفتند. - They were subjected to a reprimand regarding hygiene.

This is a formal passive construction. Instead of using a standard passive verb, formal Farsi often takes the word مورد (subject/instance), links it with an ezafe to an abstract noun like توبیخ (reprimand), and follows it with a conjugated form of قرار گرفتن (to take place / to be placed). Literally, it means "they were placed as the subject of a reprimand."

Why use this long structure instead of just saying آنها توبیخ شدند?

The moured-e [noun] qarâr gereftan pattern is a stylistic choice used primarily in formal Farsi, such as news reports, official documents, and professional writing. While توبیخ شدند is perfectly correct and means the same thing, the structure used in this sentence elevates the register and makes the statement sound much more official.

What is در خصوص and could I just use a simpler word like درباره here?

در خصوص (dar khosus-e) is a formal compound preposition meaning "regarding" or "concerning." You absolutely could use درباره (dar bâre-ye) to mean "about," but در خصوص perfectly matches the highly formal, official tone established by the passive verb structure at the end of the sentence.

Where are the hidden ezafe vowels in this sentence?