It's probably a little water mold, which will mean some of the leaves might be dead or dying. Just pull those off or rinse the plant. Water mold usually dies off in a week or so on its own, but watch it doesn't get hold of the tank too much -- or your fish.
Water mold won't hurt a healthy fish at all in small amounts, it's in all water and is opportunistic. I've had huge amounts of mold on wood, etc, with no ill results for the fish at all. It will attach to dead tissue on a sick fish, though, and then can be a real problem.
Make sure to remove all waste food quickly, as mold loves that stuff..