This paper deals with the problem of distributed fault detection and isolation (FDI) in multi-agent systems (MASs) with disturbed high order dynamics subject to communication uncertainties and faults. Distributed finite-frequency mixed H =H1 unknown input observers (UIOs) are designed to detect and distinguish actuator, sensor and communication faults. Furthermore, an agent is capable of not only detect its own faults but also faults in its neighbouring agents. Sufficient conditions are then derived in terms of a set of linear matrix inequalities (LMIs) while adding additional design variables to reduce the conservatism. A numerical simulation is carried out in order to demonstrate the effectiveness of the proposed approach.