Dragon Tree

I have 3 Dragon Trees which I bought last year all 3 are 5 - 6 foot tall, I decided to put 2 of them out side for some fresh air on the balcony. It takes 2 people to carry each one, however afer my friends had gone the trees were out side for a week and a half, I eventually got them in only to find that the long thin leaves were dropping from the trees, so I shook the trees and I ended up with bare stems. The bottom of the plant is like a small tree thick woody looking. The tops of the dragon tree have turned yellow and rubbery so I decided to chop all the heads off? now its 4ft tall and still rubbery. Is there anything I can do

 

Hope for the best, wait and see if new shoots appear. I presume the plants got frosted, if so, it depends how badly. Put them outside by all means in the summer (even then if the plants are not used to bright sunlight, the leaves will burn) but not during the winter.
One point of interest is that if the dead leaves are falling off and not staying attached, then the stem is probably still alive.