Make sure to treat any rusting or pitting with WD-40. If your clubs are really bad, try having them rechromed or refinished. Check your loft and lie. It's something pro golfers do several times a year. While most amateurs don't play enough to need to have their lofts and lies checked as often as a pro, it's a good idea to have it done once a year.
Clubs can get out of alignment through normal play.
A two-degree change in loft can mean as much as 10 yards in distance. A properly lofted set will not have any gaps in yardage. Maybe their lofts are the same. Examine where the head meets the plastic ferrule. Make sure there are no gaps between the ferrule and the head.