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Normally with bamboo, you do not prune, you dig. Bamboo spreads quickly and to maintain a contained space, anything that is outside the space is dug up. You can prune bamboo quite freely to reshape it or to rejuvenate it. It really is a plant that can take almost any abuse. Just trim away any parts that are looking a bit ragged. It will grow back more lush and full.

It is likely the light. You can give them more light by placing a fluorescent bulb near them. Just to be on the safe side, change their water completely and add just a drop or two of water soluble fertilizer.

Transplanting is hard work and involves digging a large chunk of root ball out of the ground. Never transplant bamboo when it is shooting. Dig bamboo either very early in the spring before there’s any chance of shooting or wait for the growth period to be over late in the autumn. You should look for a clump of culms that has come up in the last year or so and which includes at least three or four healthy-looking culms. Here is more information: https://www.gardeningknowhow.com/ornamental/foliage/bamboo/transplanting-bamboo.htm, http://www.bamboo.org/GeneralInfoPages/GrowingBambooIndoors.html

This article will give you some advice on controlling bamboo: https://www.gardeningknowhow.com/ornamental/foliage/bamboo/kill-bamboo.htm

It may be pruned to a more manageable and attractive size by making a clean cut just above the leaf bract. Smaller stalks will branch out just below the cut, resulting in a fuller, bushier plant. This can be done any time.

This article addresses your question: https://www.gardeningknowhow.com/ornamental/foliage/bamboo/kill-bamboo.htm