It looks like moisture trapped in the floor.

We would have to know more about how the floor was laid.

Rubber liner BETWEEN a pre-slope and a final slope OR a Surface Applied Membrane over a single mud bed.

Couple of threads on forum with same issue

Here is a link that might be useful: Shower Pan Moisture Issue 1

Another thread with similar issue.

Jump on this immediately with the builder while your warranty is still in effect.

Here is a link that might be useful: Shower Pan Moisture Issue 2

This post was edited by Anna_in_TX on Thu, Feb 13, 14 at 6:28

Oh boy. We have the identical problem. Look at my thread to see good advice. Nobody wants to redo our floor, unfortunately.

three3apples, can you please add a link to your thread. thx.

3apples - how do i find your thread?

Here you go:

http://ths.gardenweb.com/forums/load/bath/msg1214041713571.html

Ours got worse since I took this picture in 2012. Nobody wants to fix our floor, unfortunately.

Please do post how you resolve yours and, when something happens with mine, I will do the same.

Unfortunately, the ''Fix'' is to redo the shower. Do it with a different waterproofing system. A painted on membrane on top of a proper preslope will let porous materials dry out because it only gets wetted very shallowly. Or you can live with it as is until you are sick of porous natural stone and ready for the faux.

Did you see the soap scum problem in AZmom's recent thread? Sure looked like water too.