A few things to remember: Dogs don't need frequent bathes, over-bathing can dry out the skin and coat. Certain shampoos can too. If I do bathe the dogs, I use BioGroom Protein Lanolin shampoo and at dog shows I learned from an old friend to use BioGroom Mink Oil Spray-wow it makes a smooth coated breed shine! Don't forget too, it's the winter and everything is suffering from the furnace and cold air drying things out.
Diet changes (additions of oils, fats, new food etc.) will take time to noticeably see a difference. Give it at least 6 weeks.
One thing I learned too years ago was some dogs shed dandruff from stress or excitement - I have noticed it a time or so on my own dogs. So I was at a hound racing trial (chasing the plastic bunny) and this Italian Greyhound was covered in white flakes, shaking so badly but ready to go!
Another note about dandruff/coat care - brushing is an excellent way of distributing the coat and skin natural oils, and despite having a short-haired breed, in my case Vizslas, they still require occasional brushing and the Zoom Groom is a gentle rubber brush that does the job for their length of coat. As you can see by the picture below, I got a nice pile of hair from Titan (2 weeks ago) and I just brushed him again last night and got another equal sized pile of hair. His coat is gleaming and looks great even in the winter:
http://i426.photobucket.com/albums/p...1e1be168c5.jpg