Where does it look like the tank cracked?
When you say the wall (attachment), do you mean that these are wall hung toilets?
Or do you mean where the water comes to the supply valve that brings water to the toilet tank?
I have seen toilets crack when someone sits and leans back too hard.
I've seen toilets crack at the trip lever because the white metal in the lock nut, which is pot metal , grows when it corrodes. Have seen the tank crack from the bottom because the 2" pot metal nut that holds the flush valve assembly does the same thing.