The "bad problem" in the valley of the ashes is that Myrtle is run over and killed in the Valley of the Ash by the car that held Gatsby and Daisy. Daisy was driving the car, though Gatsby was willing to take the blame to protect her.
Myrtle being killed by Daisy is a more extreme case of the rich conquering the poor. Daisy is a wealthy woman who lives in East Egg surrounded by others with the same fortune as her, while Myrtle lives in misery in the Valley of the Ashes.