String 2? (bottom pair): "NA" isolation value and wouldn't provide more than 14VDC to the inverter. No information on the SetApp Isolation Status page. (For reference, the functional second inverter indicates a value of 11,000KOhm isolation value)
Both strings offered up their proper idle voltage, 14 and 12VDC respectively - corresponding to the number of optimizers on each string so I think the optimizers are okay.