Update I reckon after running the fixture for almost 7 months. LEDs still going strong, no burn outs.
I finally cut the heat sink fan leads off of the LED terminals & wired them separately to the power supplies. A whole lot of cutting, soldering & running more wires to feed 27 fans, but now the 12 volt fans are getting at least 10 volts DC regardless of what I do with the LED dimming controls. The issue of giving the fans a kick start in the morning with my finger due to low voltage delivered to LEDs is now solved. Reliable start of the fans.
Note the way the emitters are wired above, with the fan leads soldered in parallel with the LED leads. All the fan leads have been cut & rewired. In the future whenever I replace a fan, I'll keep the connector on as shown on the center LED. Stripped 20 gauge solid strand wire slides into the connector nicely, no soldering.
Coral & other livestock doing well, tank looks good, saving electricity, evaporating less water. Downside I guess is the heaters need to run longer to keep the tank temp up.