Originally Posted by echinosum

I didn't know you bought them from a reputable supplier.

OK, I guessed wrong. What I said has been the answer to every one else's "why is my black bamboo dead" question, but as you can see I wasn't totally sure from the distance shots.

Black bamboo does tend to defoliate in the winter in the British climate, and it is very late into growth in the spring, could even be end of June before it does anything. So maybe you just wait a few more months to see if they are OK really. It's been really dry where I live the last 6 weeks or so. If it is like that where you are, and stays like that, water them regularly and abundantly, as they are fairly new into the ground.