How many shrimp do you have?
How big of a tank is it?
Is there anything else in the tank?
Ghost shrimp probably shouldn't be fed flakes since much of it will dissolve and polute the water/gravel. Sinking shrimp or algae wafers would be ideal for them, as long as they're fed a small amount.
My Amano shrimp eat the leftover shrimp pellets that my Zebra pleco eats and they have enjoyed them for the past three years