Hi Toine,
The normal OSP lovin: You Rock!
Actual feedback disclaimer: As always, your mileage may vary. These are simply my opinions based on viewing with my calibrated monitor. I realize that web compression enhances contrast and can have a negative effect on images. You still rock.Now, with that out of the way...
On #1 and #3 - the web images show blown highlights on the left shoulders. Possibly in #5 also - but the B&W conversion makes it harder to tell without me loading PS. Your key appears to be slighty hot on the rest of the studio shots. Easy fix. Your hairlight looks good to me, and I'm assuming a reflector for fill on camera right looks good for lifting the shadows slightly on the rest of the studio stuff (as in #3 and #4).
On #2 your flash is a bit too strong - it has gone from providing fill, to being the main light without balancing with the ambient.
I make no claims of expert status on any photographic technique - so perhaps more informed readers will also take the time to give you some feedback!