Hair dye: Nasty smell?

Hey guys, so I dyed my hair back in December. I've had it dyed plenty of times before, every time by a hairdresser and there's been no problems.

So the other day I washed my hair, same shower I always use with the shampoo I've been using for a good few weeks as well, and my hair smelled quite bad after. It smelled like dye and when I dried my hair the colour had changed from a dark brown to a more red brown.

Now each time I wash my hair it still has the smell, though thankfully the colour is ok. Does anyone know why this would happen? Or what I can do to stop it? I've tried using another shower and a different shampoo but the result is the same.