Hi @EmilyNg,
Welcome to the Bunnings Workshop community, it is fantastic to have you with us.
It is sometimes possible to conduct repairs to minor cracks in tiles; however, yours appear to be structural cracks that extend the whole way through the tiles from one side to the other. Unfortunately, there is no way to effectively repair this kind of crack. They will need to be replaced.
This kind of structural cracking occurs when there are gaps beneath the tiles, often because of poor coverage of tile adhesive. When replacing the tiles, you need to ensure there is uniform coverage of tile adhesive beneath the tiles. This is done by applying the tile adhesive with a notched trowel.
Please let me know if you have any further questions.
Jacob
