Well hopefully the leaves you've had a problem with which are showing discoloration are the lowest leaves and it's just normal leaf loss. The only slight worry is that there is obvious liverwort or lichen growth on the soil, which indicates this plant has been in its pot for some significant time period prior to being sold, and has likely been kept too wet, which might mean a fungal issue. It might also indicate the soil its in is not particularly free draining, assuming there are drainage holes in the pot, but more likely the plant may need potting up into a larger container. Otherwise, the plant looks pretty healthy, though you might want to remove the liverwort - just pick it out with your fingers. In future though, do not use washing up liquid, whether its eco or not, to clean the plant - a soft paintbrush or make up brush will take off dust, and you can then use just plain water and a soft cloth.
Don't water until the surface of the soil in the pot feels dry to the touch, but not so dry it's shrunk from the sides of the pot. When you water, water thoroughly, allow it to drain down freely and empty out any outer pot or tray 30 minutes later, and again if necesssary 30 minutes after that if more has drained. Assuming you are in the northern hemisphere, this plant won't be doing much more growing until spring, so if possible, it's better to wait till spring, around May, to pot up into something larger (using new potting soil), though if you can see lots of coiled roots hanging out of the bottom of the pot, it will need to be done now. It requires bright daylight, but without direct sun, and keep it away from heat sources. Further care info here https://www.houseplantsexpert.com/rubber-plant.html