Do you have planks separating in the middle of the floor or are the gaps opening around the edges?

That’s supposed to be a floating floor and not glued or nailed to the subfloor.

If this is intended as a “wet” room where water is expected on the floor and sloped to a drain, there should be a waterproof membrane between the sub-floor and the finished tile floor.

Either the membrane has a leak or someone skipped an important step in construction.

What you are dealing with is a heavy clay topsoil. When this type soil dries out it shrinks. It’s because of this shrinkage that you have a gap along your foundation. The other clue in the photos is all of the cracking in the soil surface, another result of the shrinking.

I wouldn’t use bagged “topsoil” from a big box store to fill in the gap. It’s mostly compost and will remain quite permeable to moisture.

You are better off amending the soil in the area with organic matter and sand to break up the clay and make sure it’s graded to drain away from the foundation. Breaking up the clay should help the soil retain enough moisture and prevent shrinkage.