Yesterday my larger male ate a whole earthworm (unchopped) and loved it. Introduced fish today and no one ate it. Little male still uninterested in earthworms.
That smaller ray may just have a problem with the size of those worms, I have an 8" Henlei who eats whole red worms (although she prefers shrimp) but doesn't attack something that size. Maybe worth looking around for red wrigglers.
Video of my new girls being acclimated. They are on and off active, just like the boys are inside the tank. They even ate a little bit of blackworms for me. Good girls!!! They are about 4.5" ... look smaller from way up here ^_^