v1rtu0s1ty

Maybe
a) too much water
b) too much fertilizer
c) not enough sun
d) bad soil
e) multiple transplants. This is just a guess :P

Honestly, the only time I maintained my basjoo was the first month after I planted it. It was even stressed badly since I planted it on an area which gets 8 hours of sun. Now, I don't even take care of it but I water it deeply once a week or maybe even 2. My thinking is that if I do this, the plant will try to search for water by extending their roots deeper. Don't follow what I am saying since it's my first time too to grow basjoo. So far, mine is healthy and I've been lucky.