I never feel comfortable giving advice or critiquing someone else's work because I do not know what limitations they are working under.
But since you asked.
My first observation.
Can you get the cameras for single shot closer to their shoulders?
They seem to look way off camera on singles.
If you imagine an interview with single subject you try to get the interviewer as close to the side of lens as possible without them sneaking into shot.
The same situation should be created with 2 person interview.
The eye line should be just off camera.
The camera angle should be as close as possible without getting into other camera's shot.
I would suggest a fill from the direction of center 2 shot camera, but that will light up your background.
If you are locked into the dark, black background and you have the budget and time, I would suggest pipe and drape- black drapes.
Charlie Rose style.
(I find the single camera shots are similar to yours and the faces a little too profile for me, but that is my taste.)
Are your key lights also working as your backlights?
If yes, you need to use net flags to take them down in intensity where the lights hit the heads and shoulders. For talent with no hair use a silk flag.
If possible it is more efficient to have the keys as keys only and to have separate small units as backlights.
These can be dimmed to taste.
These suggestions are limited to you having access to grip gear.