will take and post pics tonight.

Sounds like too much water during the Winter months. The leaves should become deep green again after temps rise and nights are also warm.

Kt

Nitrogen is my guess. Depends on how you 'organically enriched' the soil. If you didn't use completely 'finished'
compost the decomposition process will use the available
nitrogen in the soil leaving none for the plants.
I also agree with the above post, in winter they shouldn't
need much water.

riegersteve-
A clarifications for you...
The existing culms (not columns) will not grow any taller than they are now. The only way you will get more height is when new culms come up, which could be this year, or maybe the next. When bamboo shoot and put up new culms, they reach their final height and diameter in the growing season. They do not grow like other plants you may be accustomed to.