I'm willing to bet that they are looking abit yellow and dying because of the freeze we had back in January. They tend to defoliate and go yellow in too much cold, and should bounce back with new foliage when it warms up a bit. I'd wait until the end of the month to fertilize, then give them a quick acting liquid fertilizer. The pots you have them in sound big enough, although you may need to divide them and replant half in about 2 to 3 years if they grow well. They like all the water you can give them once it warms up again, so don't let them dry out.

Even when it doesn't rain for a weeks at a time in winter, they should be just fine if they are still getting drip irrigation during the winter. This bamboo only stays fully green where it doesn't freeze and they aren't subject to lots of cold, drying winds.

I've been reading about bamboos today and I can't tell you where exactly I read this but I did read that Mexican Weeping Bamboo is very sensitive to OVER watering. I've not grown it yet but I did read that somewhere today.

The Mexican weeping bamboo (is it Otateo 'Aztecorum') really wouldn't have grown much over the last several months, as it's a subtropical bamboo and growing/shooting season would have ended with the warmer weather. I agree that the yellowing may be from the cold, but it's also possible that it's not getting enough water. It should be watered like a lawn (since it's a grass); about an inch a week. The size of the container is another candidate but you mentioned that it's a large container. Any bamboo in a container is more reactive to climate issues than bamboo in the ground, where it will better thrive. It's a non-invasive bamboo, so don't be afraid to put it in the ground if that's an option. Some yellowing and defoliation is normal and it may just get happy this spring. But consider: size of the rhizome ball relative to the container, temperature (cold), water (too much, not enough) and transplanting. HTH, Jayne

Thanks for the helpful suggestions! I will make sure it's getting enough water and wait for the weather to warm up and see if that perks up the plants. It really is a beautiful bamboo - I can't wait to see how it looks after it's grown a bit.