Well, common advice goes like this: "The closer the light, the softer the light." Well, in one manner of speaking that is true, but in another manner, it's utterly wrong. If a light is very close to a person, the rate of fall-off is EXCEPTIONALLY RAPID, as in the shots of the boys...from exceedingly over-bright, to full, detail-less shadows--within just, literally, inches.
On the shot of the baby: the light is close enough that one side is overexposed, so I'd say move the light farther away, which will make the degree of fall-off from one side to the other very minimal.
A light that is 8 inches wide x 36 inches tall demands very critical aiming, and at close distances, it is going to light up some areas, and other areas are going to..."go dark". I'd be tempted to bounce the flash off of a wall as a main light, rather than use a strip box as a single,main light. Doubly so if I had to work with no modeling lamps to guide me and allow me to preview the lighting effects.
When using a small light source, or a hard light source, the exact, precise placement of the key light in relation to the subject is critical. Even a little bit off, and you can easily plummet directly into the catastrophic failure zone, much of the time.