This is quite common with hand woven rugs. Look closely and you'll most likely find it is just the black that has faded to a grey colour. As the weaver reaches the end of the rug there is often wool left over. It can't be used in the next rug because the shade will not match the next dye lot. To save wasting the yarn they put the wool into a pot and re-dye it black. To fix the black dye they need to wash it in a mordant. If they don't do this properly the black will fade quite quickly. You can see the effect of this if you have bands of different colour running across your rug. If this problem bothers you, we can re-dye the faded part of the rug.