What is the optimal light level for most plants?

I'm raising strawberries, spinach, and tomatoes in the basement and I switched from grow light fluorescent bulbs to a fan cooled LED multicolor system. The light with the old system was below 20k lux but with the LED system I'm at 46k lux. I initially tried over 50k but spinach would not grow to any size. As I pulled the lights away the spinach is now growing quite nicely and has good flavor. The strawberries taste wonderful and they are blooming like crazy. The tomatoes are starting under the fluorescent lights at 23k lux.