Cracked floor tiles in Texas

[Flygirl27]

Our house is approx 20 years old. Over the past 2 years or so hairline cracks have formed along two sections of our bathroom floor tiles. They are growing longer. Could this be a problem related to the original installation, or is it more likely a substrate issue? I’m wondering if the concrete slab underneath has cracked. What do you think and can anyone give advice, please? We are in Houston, Tx.

 

[Slippery]

I'm guessing that the substrate has cracked, they should have been laid over a decoupling mat or laid over boards.
Could be thermal expansion or subsidence.
They look like Travertine which is very soft and brittle, I can't recommend a cure, think the floor will need redoing

 

[Flygirl27]

Bummer! Thank you for the insight, that’s helpful.