(Reuters) -Belgian supermarket chain Colruyt on Tuesday reported a 25% decline in its full-year earnings, citing high inflation, declining volumes in food stores and increasing market competitiveness in both prices and promotions. Although discount chains are gaining market share as shoppers look to save money amid record inflation, for some the promise of lower prices now appears to be a disadvantage as they struggle to pass on rising costs. Colruyt, known for its discount supermarket chain, said its net profit fell to 288 million euros ($299.98 million) in the year ended March 31, against 38…