Acidic products will etch marble. First go through what you use in the shower. Does your husband shave in the shower? Check his products also. Buy a cleaner for marble and have it for your cleaning service. Though, I would think they would know how to clean marble. But maybe not. Watch out for chlorine bleach, while it is basic and not acidic, it will mess with the color of your grout. Grout will absorb water, it's not water proof, but it should dry out also. Is your darker grout on the floor? Is is possible that whoever built your shower did not built a proper pre-slope? Though, I think different methods are used in different parts of the country, but the shower under the tile should slope towards the drain. Pictures will help once you get them loaded. Here is a link that might be useful: How to post photos on gardenweb

Thinset at that thickness for your application with a breathable stone install cures in less than 30 days with a thinbed shower pan like you have . It should have initially been given a full cure prior to introducing water(after grouting). There is also rapid set thinsets that cure faster and theres also the wrong type of adhesive such as mastic or PRE mixed bucket grade glues. we dont know what you have. Dont be fooled by misinformation from some novice sales people on here about 2 months. If you want to verify if you have a grading/pooling issue as the cause. you stop using the shower. For at least a handful of days and perhaps put a dehumidifier in the shower to fully dry it out. it will either dry out and clear up or not. only time will tell. Since you have a thinbed pan you arent hurting anything(unless theres a pan leak not verified ) and best get used to it. The only other issue could be poor application of the wrong type sealer in that particular spot also not hurting anything. You chose a fickle material for a shower floor. and now reap the rewards. and you never clarified the flood testing process which is the only way to catch and correct a poor shower pan install before leaving a client with a wet mess like you may have...

Strong statement. The rest of the room should be a soft white tile with soft white walls. Let the floor stand out. Everything else white, except the faucets and hardware. You might consider those to be a matte black. The layout and shape of the white tile is unlimited. But, I'd always keep it a neutral color with the same color as the tile grout.

@kasmit00 - same!! I’m still ordering samples but getting close. I don’t think I’ve ever been so indecisive in my life! I am sticking with porcelain with just a marble accent. Too many horror stories about marble showers that leaked or were destroyed by small cracks, leaks, rust, etc.