On the off-chance that someone encounters the same issue as I did…
After I first set the damage sprites up, I noticed during play-testing that they were being positioned slightly off centre when hit, so the blocks appeared to be moving “down” on hit.
To fix this, I opened the sprite settings, and changed the pixels per unit to 128 (to match that of my block sprite), and changed the Pivot setting to bottom to match the block sprite too. That fixed it.