Do my wall tiles have water ingress? (Photos)

[Nightmaretiles]

I have started to notice a wet pattern look on my Porcelan_osa Marmol Carrara Blanco bathroom wall tiles. I have looked at unfitted tiles and I do not believe the grey ‘wet’ looking patches to be a part of the design. Quite a lot of tiles display this pattern but not all. Also they are scattered all around and not necessarily just in the shower area. The tiles were professionally fitted and I am not sure if I am seeing things or this is a cause for concern, but I am nonetheless extremely worried and would appreciate your input.

[aeromech3]

My old eyes say Yes, but I would expect a damp smell and feel to qualify what I see; can the stains be removed with a cloth damped in say Flash with bleach (read cautions) if cloth shows stain after then you have a problem.
Maybe the glazing is breaking down, perhaps from harsh scrubbing or chemicals.
Alternatively most hair skin conditioners use a type of protein which algae etc love to grow on and poor cleaning can result in what you are seeing!
How old is the tiling and what type of wall is it attached to?