Once upon a time, a diamond engagement ring was a powerful symbol of social status: the bigger the rock, the greater its cachet.Today, ring owners posting in social media forums will often voice a different sentiment: "Does this look too big?"The diamond industry has undergone an unprecedented shake-up in recent years due to the exploding popularity of lab-grown gems.SKIP ADVERTISEMENTThe price of a one-carat natural diamond has more than halved since the start of 2022, according to US industry data.Last month, De Beers — the company that helped define the diamond industry and monopolised it for decades — suspended production…