I have ordered a number of plants, and some seem to be thriving. What I am finding is that the plants were completely black, no root stem, no growth, no green, and they were dead. They were shipped green. I tried to pull off the black growth and get new growth, but they died after about three or four days. I brought all the plants that were viable inside, and nurtured them on the kitchen table. I am getting new growth, but it's dead on the bottom. Three of the plants have turned to mush in my hands.
I am assuming the plants were green when they arrived, as the plants are always healthy when packed.
The trip in a dark box does stress plants, especially if the delivery takes longer than promised by the delivery company. When it is hot, the plants will also try to grow inside the box and in the absence of light produce very soft growth that fungi and bacteria have no trouble attacking. It means that the plants have to get an airy environment and be given more light in a fairly rapid time-frame. Not too much right away though or you will burn the etiolated, tender plants. You also have to make sure that the plants are never soggy wet, since this is another environmental factor loved by these micro-organisms.
Once a black rot, a bacterial (if it stinks) or a fungus disease (no odour) is in a plant and pot, it is very hard to stop. You could try dusting with sulphur powder and water with concentrated chamomile tea or tea tree tea (Melaleuca alternifolia).