HONG KONG Gold and silver sank for a second day on Wednesday, bringing a rally in the precious metals to a juddering halt. Bullion has seen an eye-watering run-up since the turn of the year, helping it climb more than 60 percent and hitting multiple records, with observers suggesting it could soon hit $5,000 an ounce. The rally has been built on a range of issues including a weaker dollar, expectations of interest rate cuts, falling bond yields and central bank buying. But the buying reversed