Generally speaking, when you see surface mold it's indicative of a broader issue worth investigation. Clean the grout that appears moldy, let it dry for a few days if possible, and see if that fixes the issues.

@DD . It is like 15-16 months old. I do not know what water proofing system. I am trying to determine how big of a problem I have.

Could it just be rust from iron in the water? Our grout gets that look from our well water.

@mojavemaria . but what about the black spots?

How is the ventilation in your bathroom? Has the grout been sealed?

@Kate . Ventilation has been poor. Unsure on the grout sealing, but it looks like it has been cracking in other places (so I am going to go ahead and say it probably isn't.

Maybe start with some good ventilation and sealing the grout? Using a sgueegy after showering also helps a lot. Anything to keep humidity down. First clean it up, i use full strength bleach and a tooth brush.

I think Kate’s ideas are great. We live in a dry climate with well ventilated bathrooms so even our 25 year old tile on green board didn't look bad!

Who did that caulk bead? Is that over grout? This is new construction as I see you have another post going?

@millworkman . A handyman did the caulk that has the black spots on it. I am not sure if it is over grout. I don't think so?

Looks like it was laid by Ray Charles, that is awful. It needs to fill the gap between the floor and wall tile. Not sit on the surface, that as shown will do nothing.

@millworkman . What would you suggest? Re-caulk? Regrout?

All changes in plane are required to be caulk, not grout. But just because that is just a nasty glob of a bead of caulk I would definitely remove it and look what is behind it. If there is grout there it needs to be dug out and recaulked. with 100% silicone.

@millworkman . Do you think the faulty nature of how it was applied has contributed to the mold?

Do you have any pictures of how the shower was waterproofed BEFORE the tile went on?

@cpartist . I do not sadly.

Doesn't help as that glob just lets water sit there.

Obviously a professional didn't do this installation. Many things done improperly can contribute to this mess. It is possilbe the problem is under and behind the surface. We are all guessing though. If you cut the caulk out and see moisture underneath, that is one indication of a more invasive problem. Start there. Cut out (no mositure underneath?), clean, disinfect, and keep ventilated and over months you will have better information. This is only IF there is no leaking signs in room below, adjacent, or outside of shower. Moving forward, recommend you hire a qualified installer. Some resources here from The National Tile Contractor's Assn. for consumers: https://www.tile-assn.com/page/trade-professionals-consumers

@Dragonfly Tile & Stone Works, Inc. I sent you a message. Are you referring to the all of the tile or just the caulking on the shower floor?

Kyle, We responded to your message.