Can't figure out what this is?

CGD nylon 15 years old. This is not flood damage.

Hotel

I would say that the traffic area is to a washroom. I would also say the floor behind gets scrubbed & waxed very often. check what the backing is on that 15 year old CGD. I would hazzard a guess that something is wicking from under the walls. did someone use gallons of water to strip the wallpaper or to wash the walls at one time?? In that enterance take a good light and rule out any shadows I believe it is called metamarisim. But Lee will clear this whole matter up in seconds?

   Metamerism is the situation where two color samples with different spectral power distributions appear to be the same color when viewed side by side. A spectral power distribution describes the proportion of total light emitted, transmitted or reflected by a color sample at every visible wavelength; it precisely defines the light from any physical stimulus. However, the human eye contains only three color receptors (cones), which means all colors are reduced to three sensory quantities, called the tristimulus values. Metamerism occurs because each type of cone responds to the cumulative energy from a broad range of wavelengths, so that different combinations of light across all wavelengths can produce an equivalent receptor response and the same tristimulus values or color sensation. Two spectrally different color samples that visually match are metamers.

has that already been cleaned?  Or is that the before pic?  

That's todays pix of Dunsmuir and I haven't done it yet Ron. I think it has been cleaned since the damage.

Through the whole hotel?