I cleaned the concrete balcony when it was raining, just poured some water on it and went at it with a brush, I wouldn't even say I used a lot of water. Now there's quite heavy staining, especially where there are cracks, and they don't seem to have improved. Most of the floor dried up fairly quickly but it has looked like this since 3 days now.
The concrete is porous and will suck up water and anything that is in the water.
You should consider something to seal and cover the surface.
Tile, epoxy coating, even a concrete stain or paint. You will continue to have the uneven look you are fighting and dislike unless you get the floor sealed somehow. As a bonus keeping water from seeping into it will help the structure.