I feel I should also point out that often bird keepers make the mistake of thinking "it's ok for a bird to have it in the wild, so it's ok in captivity" But two factors come into play: Environment and instinct.
Birds have a far more varied diet in the wild and access to digestive aides like natural clays which also aide in detoxification. We can't even begin to presume we have the ability to replicate that. Also, the amounts of edibles are drastically different as well. A wild bird who chews a wayward leaf here and there is a far different matter from a captive bird that has regular access to the same type of leaf.
Eucalyptus is also very aromatic so keep an eye out for respiratory issues, and while originally dry, I would be worried that the moisture and bacteria from the bird droppings would rehydrate the leaf and promote mold or mildew in their living environment if not changed frequently.
Also our birds are several generations removed from their wild relatives (with a few long lived exceptions). Their instincts aren't as sharp, and captive birds are prone to anxiety driven behaviors you'd never witness in the wild (excessive chewing, plucking, repetitive stress behaviors, etc.) that preclude self preservation. A captive bird wouldn't know a poisonous plant from a tasty treat, and it wouldn't recognize warning signs for such either that would cause them to stop in the wild. It would just see something to help it stave off boredom.
Anywho, let me know how the crystals work out, I'm interested to see what results you get.