I painted the living room/kitchen in my flat light blue and white about a month ago (2 coats of white for the white walls and 1 coat of white and 2 coats of blue for the blue walls), but today when I went to wipe a little mark off the wall, I noticed the cloth was also wiping the paint off. Further investigation revealed that if I touched the walls while they were moist at all, it would leave paint residue on my finger. I did a little more testing and with only a little effort I was able to remove the paint to reveal the previous coffee coloured paint. In contrast to the coats I applied myself, it was only possible to remove this layer with a lot more pressure on the cloth. All the paints are Dulux matt emulsion, so I don't really understand what the problem is. Any advice would be appreciated.