The problem you have is called efflorescence which occurs when any concrete product is over washed before it is cured.
Shower floor grout turning white.
But on grout and shower curtains pink mold is really just a cosmetic issue.
My shower floor is the same type as this person s i don t have that odd white discoloration though and no cracked grout along edges.
This is a natural phenomenon called efflorescence.
A week later the line turned white.
The most common reason is moisture from the ground below the slab but grout may also turn white from the rain in outdoor installations or in rare cases from water used to clean the floor.
Some caution must be observed in selecting the sealer.
Rather this is similar to the whitish haze seen with floor wax when it is applied to a damp surface.
In january 2017 i noticed a dark jagged line about a 1 4 inch wide on the pebble shower floor from the middle of the shower door opening at the top of the floor pan to the drain.
Answer when there is a white haze on a shower floor it is normally either efflorescence precipitation or you have trapped moisture in the tile assembly by applying a non breathable sealer over the floor.
They have an efflorescence remover on the market but they only work so well with grout.
Another possibility is that grout containing polymer was used and exposed to too much water before the polymers had a chance to combine.
Under certain circumstances a white powder can form on grout especially on floor tiles.
When they dry out on the surface the remaining salts appear white and powdery.
Grout turning white can be caused by efflorescence which is the calcium from the water and the underlying concrete or mortar migrating up through the porous cementitious grout.
What i do have though is darkened grout near the middle of the shower size of a dinner plate.
It is due to soluble salts rising to the surface of a cement based product.
Make sure that you get a good sealer onto that grout before you get after it again with water.
The bacteria grow on surfaces that stay damp for long periods especially where there is also soap scum.
Topical sealers acrylic sealers which coat the grout joint and are not vapor permeable may turn white from reactions between the acrylic and moisture.
So no you do not have to remove the grout.
This is not efflorescence.
Known as efflorescence white stains appearing on the surface of tiles is caused by water penetration underneath stone or tiles.