After almost a year of trying to grow microgreens for market and failing with each batch, I've finally had success.
By using a mixture of coconut coir and perlite, and by placing my 10x20 trays in the natural sunlight of a temperature controlled greenhouse, my test trays of spicy radish microgreens and mild kale microgeens flourished into a healthy crop in 10 days.
A test tray of sunflower microgreens is showing much better progress, but has not yet produced the results I'm looking for. I think that I have kept the growing medium too moist and a little bit of damping-off has occurred.
I don't know if it is the sunlight that has brought about the desired results as compared to the artificial compact fluorescent lighting that I had been using before, or if its the fact that I have abandoned Sure-to-Grow brand growing pads in favor of a more traditional growing medium.
It could be also a combination of these two which have produced a wholly improved growing environment for the microgreens.