This week i noticed that my dog has dry skin, she even has dandruff

i don't know what 2 do!! i use the yorkie splash shampoo, conditioner n detangler (which i love

) n i have been using those for about 3-4 months, i also give my dog the dream coat supplement by halo.. so i dont know what the problem could be

The food that she eats is INNOVA which has lamb as the main ingredient, she has been eating that for about 4 months now.
Does any1 know what i can do to help her skin?? she scratches from time to time, she doesnt have any flees... is there any product that i could buy to help her moisturize her skin?