feeding help

i have bought a variety of foods for my fish because i know that the need a well balanced diet to be healthy. the problem is my jack dempsey will ONLY eat blood worms and my gold saum will only eat blood worms and flakes, the convict eats anything but pellets. the foods i have bought are : TetraMin Flakes, baby shrimp and granules --- Hikari Cichlid Gold pellets --- Topfin small cichlid pellets (floating and sinking) --- Wardley Krill/Aux Krills --- and Omega One freeze dried bloodworms. im just getting concerned because i have had these fish for about two weeks now and i know its not good for them to eat only one food, especially the dempsey who will only eat the worms, but the gold saum only eats worms and flakes so im sure that isnt very healthy either. All the fish are small, between the sizes of 1 and 2 inches and im sure i break up the food nice and small for them, but they wont eat it. So i guess my question is does anyone have any tips on how or what i should try. i just dont want them to become sick from an un-balanced diet, so please any suggestions would be greatly appreciated. thanks