This is bad, I do not know anything what could stop derubberizing process. Temporarily you could help yourself with talk (children powder) to apply it on the black side of curtains and maybe as well on red side, on places when black rubber penetrated through. This shall prevent stickiness, but will not stop the process.
Some years ago MicroTools was selling red curtain fabric, unfortunately I did not bought it then. I was not able to locate any source for red curtain fabric now. Shall any RFF member know the source, pleaseeeee