Answer: Based on the information in your question I assume your bamboo is in a container. Bamboo loses some foliage year round, as the older leaves are replaced by new ones. But this would be a slow process, not an abrupt one. Overall yellowing can be caused by over or underwatering, so perhaps the watering was uneven while you were away. Yellowing can also be caused by lack of nutrients. Bamboo needs an ongoing supply of nutrients when it is in active growth. If you are not fertilizing regularly, try a complete water soluble or slow release fertilizer such as 10-10-10 plus minors used according to the label directions. If the yellowing is due to lack of nutrients, it should turn green again. I hope this helps.
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