You forgot to put the topazes into the Cube before clicking Transmute.
This causes the Work of Cathan recipe to be used instead of Caldesann’s Despair.
That recipe removes the level requirement on the item.
You can tell this is what happened by looking at Wizzy’s gear in the armoury site. Hover your mouse over your helm, and compare it against another piece of the set…
This is covered in the stickied thread at the top of the forum…