I'd just let it do its thing. I have some indoor bamboo that shoots unpredictably, and I just let it grow. If you don't like it when the shoots get to their full height, you can always prune it then. Remember, though, that culms have a certain lifespan (maybe 5-7 years) and then die, so those 3 existing culms aren't going to be around forever. Think of the new shoots as replacement culms.

thanks for the input,I'll let-em grow.