AC/DC converters today use switch-mode power supply (SMPS) conversion techniques and use many magnetic inductors and transformers driven by MOSFETS or power ICs. If your AC/DC converters were subject to a very strong magnetic field while operating, the external magnetic field could have caused the internal inductors or transformers to magnetically saturate, and this would have damaged the MOSFETS or ICs driving the magnetics.
Photo couplers or optical isolators would not have been directly damaged by external magnetic fields.