Orange black stuff on SPS

[Palmer]

Hi there,

I have some orange/light brown and black stuff growing on my plating montipora and purple digitata. I noticed something a long time agao and it seems to be growing slow but noticed it has spread quite a bit. It seems to kill the polyps wherever it is at. And it appears orange on both colored corals which are next to each other. Any thoughts on what it is?

thanks,

Palmer