Small terrestrial caudates are notoriously difficult to feed. In water, newts rely on smell, in addition to movement, to identify what is "food". On land, they make less use of smell and are more dependent on movement as a cue to finding their food. If the pieces of worm aren't wiggling, the newts may not recognize them as food. If they still haven't eaten the pieces in a couple of days, try putting the worm bits on a toothpick and holding the food in front of the newts, at eye level or lower. This may take patience, but they should eventually eat this way, though it may take several attempts until they accept it.
Your other options would be to get live flightless fruit flies or pinhead crickets or bugs from outdoors.
