Do you know the temperature of the water? Remember goldfish are cold blooded so their metabolism will slow down (digest their food more slowly and will be less hungry) if the water temperature is low.  This is  completely normal for goldfish.

Another thing i would keep an eye out for is any sign of illness on the goldfish, especially if they were recently purchased. Look to see if the fins, eyes, and scales look normal and healthy. Also watch to see if the fish are swimming ok.

Sometimes it will take them a day or two to get used to a new environment before they start eating. Use high quality goldfish food from name brands such as tetrafin goldfish flakes, wardleys, etc..

my goldfish seem to love oranges! if i drop them into the water they start nibbling on it around 3 minutes later. Oranges provide essential Vitamin C. Also, my fish enjoy romaine lettuce, shelled peas, pumpkin, and spinach (eww).