A change in dishwasher detergents that became final in 2010 may cause some changes in your kitchen. The new formulas lack phosphates, chemicals that are bad for the environment, but good for cleaning. Check the package and try something new for a change. Your old cleaner may not have been reformulated to replace the cleaning power of the old ingredients. Does your old cleaner seem as effective as it used to? Do you seem to use more to get those dirty dishes clean?
Consumer Reports, in September 2010, generally scored tablets and packets higher than cheaper powders and gels, but it said new products are still evolving. Rinse aids help, and are often combined with detergents in the newer products. If you spot spots, it's time to change.