Some of the problematic ingredients include lecithin, corn syrup, rice and peanuts. An example is an Israeli halvah sold in the Passover section of the supermarket. It contains corn syrup and therefore is kosher for Passover only for Sephardim. This year stuffed grape leaves from Turkey are being sold with the Passover products. This product contains rice and so is only kosher for Passover for those Sephardim who use rice on Passover.
Marshmallows are a product with problems.
The main ingredient of marshmallows is gelatin, which in most of the Passover marshmallows on the market is made from beef hides from non-kosher slaughtered animals. This is a controversial ingredient that the major Orthodox Certifying agencies in the United States do not accept as kosher. You should consult your own rabbi. . The gelatin is in them made from glatt kosher kosher slaughtered beef hides. On Passover, even the type of oil used becomes important, since the standard corn, canola and soybean oils cannot be used.