Typically: Workmanship or material issue. You see, when tiles are laid they are soaked in water and even covered w wet newspaper to prevent them from drying out too quickly.

Wetness from flood does not affect cured tiles, else everyone’s bathroom will already have popping tiles after a shower.

In your case: because of the flood during curing (28days after laid) ⚠️ it already diluted all the cement and susu leaving a very weak bond hence 🍿 tiles