Unhappy with veneers - very yellow in between. Why has this happened? (Photo)

I had 10 porcelain veneers put on as I wanted a "perfect" smile. In between my veneers it's very yellow and I can see where they are stuck on. Why has this happened? My dentist says he will redo all of them in 2 weeks but I'm worried they will be botched again and will be unfixable after. I also have a gap between my two front teeth which I never had before and I can feel air and saliva pushing through gaps in my teeth when I talk which was never an issue before.