Re: Basjoo leaves browning, spine of leaves going black?
The brown edges of the leaves appear to be from over watering. The base of the leaf in the 1 st photo appears to have been eaten by a bug and enlarging the photo I think there are several bug bite marks. This may be the cause of the black in the mid-rib. ... when you shake the plant do you see any flying bugs? ... Anyway spraying to control sucking bugs will not hurt the plant. Also, look down in the top of the pstem for any worms/larvae.
The leaves of the plant have folded down. High heat (100 + deg F), lack of water or root damage (lack of water & nutrients) are the cause of this. Root damage can be from insects & nematodes. So check the soil.