Follow up on new system

Here's a follow up on my system. Most plants are doing pretty well, specially arugula. Roots on these reach over 8in and are growing fast. Lettuce now started to take of as well. I think things will move exponentially from now on. I have several seedlings waiting in line, arugula, lettuce and spinach. I also purchased new seeds for these from a different source to see if will make any improvement to next cycle.
I now lowered the lights to 21in over the plants, 100% power.

Here are few pics:

Added a small fan to circulate air in the system

Added this modified water cooler with a temperature controller to cool the nutrient solution. I was getting over 75F and now it stays under 72F.

Here's the reservoir showing the large black pipe for the system and the smaller vinyl tubing which circulates through the cooler

Arugula

Lettuce

Spinach

Watercress