Pink slime mold. Fix your ventilation and clean the darn thing. https://www.huffpost.com/entry/pink-slime-shower-gunk_n_6793586?guccounter=1&guce_referrer=aHR0cHM6Ly93d3cuZ29vZ2xlLmNvbS8&guce_referrer_sig=AQAAAI2URzfck9Q8ssxYQFCi5Nt3ev4-PoZ_91cz-INQCgqBXz-pk3-rp1z9gsel4cktX2VCiZaFwLfiobb0JHn_zgNHaoj9dxn9L1UUAQdybrM0IXakTQ4zAsZd1ol6rwSoCHWEXXqOFrIkicsYNylj9FuUbVqqpu84TCnjAJmhHaB7

That is a particular bateria (can't remember the scientific name). It's pretty common in dorms, hospitals and such. You should clean it asap because once it takes hold it can be difficult to erradicate. Good ventilation, and drying the shower with a big towel after use (especially in the corners and niches) will help a lot

If it's pink then it's not mold, it's bacteria: Serratia marcescens. It's not limited to institutions, it's quite common everywhere.

The shower is 3 months old. I squeegee It every time I shower and scrub it with a natural cleaner with baking soda and citric acid at least once per week. I think they didn’t use sealer on the grout so it doesn’t dry out and gets the bacteria.

Sealer has zilch to do with anything. It’s insufficient ventilation where it isn’t drying out. And it’s your useless “natural cleaner” that isn’t really getting rid of the soap and dead skin cell residue too.

we used to have well water with high iron and it would discolour. any chance you have that issue also?

no photo, but if it's really "pink", it's mostly a ventilation/ drying problem.

I agree that those natural cleaners aren't useful in a shower. You need to use an actual bathroom cleaner.

All the current bathroom cleaners I can find are natural, "green", etc. Dow Scrubbing Bubbles used to have the ingredient that killed mold, etc., but the formula changed and it is gone.

Actually, baking soda and vinegar are the recommended cleaning agents for showers and grout. Vinegar is, of course, citric acid. You people are out to lunch. I did find where not only sealing the grout is important, but resealing on a regular basis is as well.

Nope, pink mold is a type of (usually) harmless mold. Often found in ice machines, and, occasionally, in showers, etc, where moisture sits and grows the pink mold. leftover skin cells and fats from soap leave a nice growth media for this unattractive mold.
Vinegar and a good scrubbing will probably remove it. I don't like bleach. It might be necessary. Try the vinegar first.
You can apply sealer to the grout after it's cleaned , rinsed, and dried. But if it wasn't in your contract, it wouldn't have been the responsibility of the tile contractor.
Sealer also will need to be renewed from time to time.
If you're getting pinkish stains, even after squeegee, try drying the areas with an old towel. You may need a better exhaust fan.

"You people are out to lunch."

Why did you ask for help here if you are going to insult the people that are trying to help you?

"You may need a better exhaust fan."

YES

Yeah not a very nice response to people who are trying to help you. Kindness doesn't cost anything.

Sorry. There were some very derogatory comments that I actually flagged as abusive and they have been removed. They implied that I had a problem because I was a slob and didn’t clean my shower or I was an idiot because I used a “natural” cleaning product. Since those are gone, others have been mostly helpful.

Nancy Ross, I didn't see those offensive posts. Sorry you had to see them.

From the websites I have read about serratia marcescens (the pink bacteria), bleach and venitlation seem to be the cure.

Acidic products do not kill kill mold. Neither does baking soda. Bleach does.

The beauty of the internet and this forum is you take the info you want and scroll past the others. Learn to have a thicker skin and scroll. The poor choice in wording makes the responder look like the bad person. Reporting in my opinion makes you look bad.

Bleach only kills mold on impervious surfaces, not grout.

This product looks like it has the same ingredient the old formula of DOW bathroom cleaner had. (I need to buy a bottle for my wood laundry drying racks). I was once told a fungicide like this will kill the mold, and bleach takes care of the stain but will not kill the spores. YMMV

Baking soda and vinegar do not clean anything. They mostly fake it by foaming up a bit, and that will carry off some surface debris. There is no surfactant to aid in cleaning. There is zero disinfecting ability. It is what has allowed the pink slime mold to thrive.

To counteract that, and actually fix the issue, use hydrogen peroxide + Dawn dishwashing liquid in 1 spray bottle and vinegar another. spray with the peroxide, then the vinegar. Allow to sit for 10 minutes. Then scrub, really scrub, with brush, and rinse.

You need better bath fan. And to dry the shower better after use. Use your towel to dry the corners after squeegeeing. That assumes there is no textured tile like beveled tile in there.

I spray and squeegee my enclosure after every shower with a mix of 1/2 cup each of peroxide and rubbing alcohol, 1 tsp. of Dawn, one tablespoon of dishwasher rinse aid and fill the rest of a peroxide bottle with water. Keeps everything clean and bacteria free.

If you don't have a nice gap under your bathroom door, so make up air can enter as your fan is running, you wont move the air out the ducting. Dry the caulking and corners with a towel daily or after every shower. Don't leave the niches damp either. I have never had an issue in the 6 years I've had my new shower. I don't squeegee, I wipe with a giant microfiber towel daily. I pay particular attention to the corners and change of planes. I keep an eagle eye on the caulking to be sure nothing is growing. Nothing is growing.

Grout is not supposed to be sealed, so that it can evaporate the moisture. At least that is how I understand the function of cement type grouts. Its the wall system that keeps the water out of the stud space. Same with a tiled floor, I believe. A question for the tile experts.

Like others have said, good venting/functioning exhaust fan, and daily thorough wipe downs keep everything looking nice.