Lith had rearranged the organic materials that comprised the Voidwalker armor so that it would fit his new body and that as the Spark refined the materials, they would have the space to grow.
On the other hand, however, the scales and bones were now thinner than before, offering a lesser degree of protection until the size of the body parts of the dead Dragon reached that of the living Tiamat.
Lith had needed to add more Adamant to coat the exposed surface of the now-stretched suit of armor. It was a subpar result by Lith's standards, but he lacked the Adamant necessary to craft a full metal Voidwalker armor for a bright violet-cored Divine Beast.
To make up for it, Lith had replaced the violet crystals with elemental crystals.
The idea was to move the previous violet crystals back into the mines where the tower would refine them into white 24/7 and leave the Spark to focus its energy solely on the Dragon's remains.