Because you have two separate identical power supplies that can output several amps of current, I would put a resistor/LED across each output. Where the two outputs are separate you will need two indicators to show that each of the two supplies is working.
If panel space is tight, maybe you could use a two-color LED? That would show 4 states...
- Off/Both Failed
- Only one color, one side operational
- Only the other color, the other side operational
- The two colors making an averaged color, both sides operational.