Hikari Vibra Bites For Picky Eaters?

Only one of my darters (a tessellated) seems to eat and not spit out the food yet...still trying to train them.

While I was on vacation, I fed all of my tanks using a battery powered feeder.  This tank had flakes mixed with Vibra Bites.  Since then, I feed my fish that combination and supplement with blackworms.  All four of my darter species will eat the Vibra Bites if they can find them before the other fish eat them.  However, not all darters eat them.  I have one rainbow darter that spits them out and one that eats them.  I have one fantail that eats them, and two spit them out.  Maybe one day, all of them will eat them.  Maybe I should stop feeding blackworms for a while.  If they get hungry enough, maybe they will all eat them.  What do you all think?

Unfortunately for my darters, the other fish consume them rapidly, with the two biggest pigs of the tanks especially fond of the Vibra Bites.  These two fish are now spoiled rotten.  They used to love the flakes, but now they ignore them and wait for me to feed the Vibra Bites or blackworms.  Who are they?  The river chub and my longnose dace.

Nocomis gotta eat and grow!