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That container seems very small for such a large plant. I would recommend replanting, and cutting off an inch or two of the bottom of the root mass before replanting. This should solve your issue.

This article will give you more information on the care of bamboo: https://www.gardeningknowhow.com/ornamental/foliage/bamboo/growing-bamboo-in-pots.htm

Your plant most likely has powdery mildew, a common fungal disease. Separate the affected plant from the other two plants to prevent the fungus from spreading, and wash your hands and any tools after touching the diseased plant. Please see these articles for control options:
http://mgorange.ucanr.edu/Weeds_Pests/?ds=546&uid=19
https://www.gardeningknowhow.com/houseplants/hpgen/powdery-mildew-treatment.htm
https://www.gardeningknowhow.com/plant-problems/disease/powdery-mildew-homemade-and-organic-remedies.htm

This, completely, depends on your location. You can start them indoors at any time, But I would transplant when there is no chance of frost in your area.

This article will help on the care of bamboo: https://www.gardeningknowhow.com/ornamental/foliage/bamboo/caring-for-bamboo-plants-in-your-garden.htm

I would need a picture to see if it was actually bamboo, or dracaena. This is often sold as "lucky bamboo". This will not survive outdoors unless you are in a warmer climate. Bamboo can be grown in cooler weather, however. Can you include a photo so that I may see what it is?

This article will give you the best selections from your area: https://www.gardeningknowhow.com/garden-how-to/gardening-by-zone/zone-7/bamboo-for-zone-7.htm

Try using bottled, or unchlorinated water with a drop of liquid fertilizer. It is likely becoming sensitive to the chlorine, and if you use a water softener, then this will kill it as well. Make these changes, and if it still does not respond, then you will want to transplant into soil. You will want this to recover, as it will not likely regrow if it is cut.