Two liars

Two kids are liars, three can only say the truth. Jane: " Julia is only a liar, if John is telling the truth." Julia: "If Joey doesn’t lie, then either Jane or John do." Joey: " Jack lies, as does Jane or Julia." John: "If Julia is telling the truth, then Jane or Joey do as well." Jack: "If you round up Jane, Joey and John, you will have at least one liar." The compulsive liars are_____