Do these look too dark?

[jeffkohn]

I think Jesus and others may have a point about the black top playing tricks on our visual systems. Typically a white background is used for high-key portraits, where you're more likely to use lighter clothing and a lower lighting ratio (such as glamour/butterfly lighting). The idea being that the picture is mostly light tones so that the flesh tones of the model stand out. In the first two pictures the thing that most stands out is the shirt, because our visual system is drawn to areas of high contrast when looking at an image. In that sense the 3rd image works better though I might consider cropping off the jeans if it were me. :)

You might try Jesus recommendation of changing the shirt color just to see how it affects your perception of the image. Alternately, try chaning the background color (that might actually be easier, plus your lighting might be better suited to a midtone background color).

I like the pictures though, you're getting better at the lighting with each round. I prefer your second set of edits particularly for the 3rd image, which in the first edit seems to have a yellowish cast.