Hello downtownnyc! I agree with Hetty, try to check the roots below. Maybe the plant has been living in that media for a long time and has compacted so you need to allow the roots to have some breather. You can mix in some perlite or pumice to make the media well draining. Their leaves tend to be dark green color most of the time since it is often grown in low light.
Also when you water this plant, water it thoroughly during the day and allow to drain. Your container has drain holes right? You will have to adjust watering as seasons change, but keep it relatively moist, not soggy. Maybe once a week during winter and a little more when Spring returns. Light levels are lesser during winter, and most houseplants even though indoors tend to slow down too in growth. They will return with better vigor in Spring.
Do you intend to keep that 8 feet height on the tallest one? You can trim that but suggest wait to do it in Spring. New heads will sprout below the cut off part. Then you can also root the top part you have removed.
