missjellyfish, generally, pruning side-shoots, suckers etc. will promote the growth of the terminal shoot(s). When the required height has been attained, the terminal shoot can be cut off. This will stimulate lower buds to grow. The canopy is developed by judiciously removing or cutting back shoots. Here are some images.

My guess is that it is severely root bound and needs to have the roots soaked. Also, it was probably grown in a greenhouse and used to high humidity. You will get a better answer on the houseplant forum, we talk about the edible fig here.

Unless Emily has confirmed there are actually 2 separate plants and not 2 branches masquerading as trunks, which are connected below the soil line, we probably shouldn't take for granted there are 2 plants. Even if there were 2 plants, it doesn't look at all like there would be the kind of competition between plants of the same species such that one would be genetically vigorous enough to hog resources to the point it would create deficiencies sufficient to manifest a steep decline in the other. I mean, there are no roots crawling over the surface of the soil, and there is no disparity in size that could suggest a larger, taller plant might be shading out its shorter, smaller counterpart - so what competition? It's not unusual for one or 2 roots to be negatively affected by disease while other roots in the same pot or even on the same plant are better able to cope with less than ideal soil conditions. The result is often the death or decline of 1 plant in a group planting or one branch on a tree. Roots do have very specific connections to individual branches such that the death of a root can almost automatically mean the death of one branch. The 1 root to 1 branch connection is so strong in Thuja occidentalis (eastern white cedar) that when the center of old trees rot completely away, you can often observe several live veins growing from thick roots, each supporting only 1 branch. Most observers would think they were observing a ring of unusually shaped trees if they came upon this interesting occurrence in nature. Given the volume of soil available for root colonization, I just can't see it being a case of one plant outcompeting another, if in fact there really are 2 different plants. I'm pretty close to certain the issue is related to root health. Al

Overwatering is the likely reason. If you’re watering on a set schedule and can still detect moisture deep in the pot, you’re over watering. Water as the plant needs it, not on a set schedule. Also, place the tree right up of front of your brightest window, not a few feet away.