Originally Posted by echinosum

I suggest posting this on bambooweb.info • Bamboo Forum which is the active bamboo forum populated by many bamboo experts, and say where in the world you are located. In the absense of reports of gregarious flowering, it seems likely to be stress flowering, as you recognise. In which case, if you remove the stress, it will likely recover. You say it's a large bamboo, you've had it in the pot a year and a half, and the new culms are small. It could well just have eaten all there is to eat in there now and filled the pot up.