Whats wrong with my guppies? all the females keep turing a really white color and then dying.?

it sounds more like a bacterial infection to me, because if it were ich, it would have not caused discoloration, instead it would have just made some white marks on the skin, problem would have been inside the fish. how many fishes do you have? if it gruppy only i suggest you get rid of them, super clean your tank, and bring in some new fish, dont' put old fish in there, diseased or infected fishes will rot the pack again.