A federal judge declined to certify classes in a lawsuit accusing a pet product manufacturer of putting out a line of dog treats that are potentially deadly.In a written opinion last week, U.S. District Judge Sara L. Ellis held the nationwide and multistate classes proposed by the four named plaintiffs do not meet the requirements for certification set out in Federal Rule of Civil Procedure 23.Three of the plaintiffs maintain their dogs became ill and the fourth maintains his dog died after eating Pur Luv pet treats made …