Hi Erik, any info helps
Well, I guess I am just a step ahead of you as I have finally witnessed them eating!
They actively go for the smallest waxworms when the worms are placed in front of them. A couple less shy ones now even eat them from plastic tweezers! (you'll find you have more control over these small worms with plastic, rather than metal, tweezers)
It seems they are more apt to eat when not disturbed (i.e. by being moved) just prior to feeding.
I have also finally had success, though less so, with small balls of tubifex worms placed directly in front of the morph.left to wriggle on the wall of the container. Depending on the size of the ball, this can make for a much more substantial meal that a tiny waxworm or two, so I hope to get more used to eating this way.
Prior to this, I had been regularly adding the smallest pillbugs and and the smallest crickets to their container, and like you and your situation, I assume the morphs have been eating one or the other of them because they are not skinny, since even before the success with waxworms and tubifex. I would still like to witness a cricket being eaten to be sure.
Have you tried fruitflies? I have access to these but haven't tried them yet.