Time for the researcher to be introduced.
She is one of the most important and recurring characters in the story, the first floor water was able to fix the most extensive damage from the illness, but acne, scars, living when hiding herself and without exercise require other floors water.
The mana/miasma in the dungeon boosts the effects of the water, it is possible to bring water from a lower floor to the first and it still keeps the original effect, but much weaker, the first floor water can be brought out and it keeps the effect, not return to normal water like the other floors, but is still a bit weaker, as she said the dungeon tempts peopel to explore it.