I looked all over the internet and cannot find what I need to do now. I have a 2 story house with 2 bathroom and a septic tank. Well the bathroom upstairs is not working. First the shower was slow to drain then the same day the toilet backed up in the tub. It was clear water but it took a while for it to drain out of the tub and the sink is draining in the tub to .we snaked the bathroom all of it and we found nothing so I called a plumber, he snaked it to but there was nothing. After the plumber came the water that would back up in the tub is a yellow brown and has an odor to it. So we went on the roof and snaked out the vent but the water in the tub would not drain so we stopped doing the vent. And now the water that comes up from the tub is black. We had the septic tank cleaned out a few weeks ago, I have done all that I can thank of and I do not know what to do now. Oh and when you turn the water on to the tub the toilet will bubble if that helps. All advice will be welcomed.