What can be done if DPOA and DNR forms were filled out when person was mentally ill and not witnessed and resident was not resuscitated in ER?

In the state of Michigan the DPOA form requires 2 witness signatures and no notary. In 2008, X showed signs of a mental illness which were annotated in notes left by some healthcare aides who visited X before X was admitted into a nursing home. X had signed both the DPOA form and the DNR form at the same during this time he was experiencing mental illness. The DNR had no witness signatures on it. Years later, X was rushed into the ER unconscious. ER informs X’s agents who both tell doctor not to resuscitate. X dies. It is later found that the DPOA form has flaws. The DPOA form had only one witness signature on it with a date of his signature being 2005. That witness had died in 2006 which was 2 years before X and the 2 agents signed the DPOA form. X’s adult children became upset and want to sue. Is this a case of negligence and wrongful death? If so, who could be held liable? The hospital for assuming daughter was DPOA without seeing proof? The nursing home assuming daughter was DPOA without seeing proof? The daughter for assuming she was DPOA?