Inside your sentence, which happens to be the subject, so no inversion can take position. Additionally, the ultimate clause is a press release, not a question: which can be operating to be a relative pronoun, not as a question phrase. A similar would apply if it had been an adverbial. Evaluate both of these sentences:EDIT: Based on a dictionary the

natural - current in or made by mother nature; not artificial or imitation; "a natural pearl"; "natural gasoline"; "natural silk"; "natural blonde hair"; "a natural sweetener"; "natural fertilizers"Recently, kibble has confronted its share of criticism, and at times, rightly so. However, not all dry Pet food is proven equivalent, and Here are a few