"What am I looking at in these pictures?"
Looking closely at the mimosa (
http://en.wikipedia.org/wiki/Mimosa), notice how the foliage slowly darkens and turns red over the duration. This is most obvious on the the edges. The only one given the dyed nutrients was the mimosa. Here is a picture of the bottom of the foliage where the discolouration is more obvious. This variety closes their leaves before the lights turn off and this is why the leaves are closed.
http://img281.imagevenue.com/img.php?image=61419_Day_8_PM_122_547lo.jpg
Here's a picture from today. Last night I flushed the cube (as much as was possible) and put the plant back in the flood table with some of the others.
http://img204.imagevenue.com/img.php?image=66521_Mimosa_122_224lo.jpg
"Plenty of hydro users are savvy enough to use RO or treated waters in their systems."
I've owned multiple reverse osmosis units. They can be tricky. You have to get the GPH just right for optimal functioning. Even the more expensive ones don't remove enough of the medium-smaller sized molecular impurities to satisfy me. I've owned two four stage units from name brands (Micron Filtration=>Carbon Filtration=>Thin Film Composite Reverse Osmosis Membrane=>Mixed Bed De-ionization) and both left detectable impurity levels that were to high for me. Even with all that filtration some medium-small sized molecular impurities pass through freely. Better thin film composite membranes exist but in my experience they are not available for non-industrial applications. In fact most residential reverse osmosis units don't even mention the mechanical selectivity of the membrane. The only satisfactory solution I have discovered is fractional distillation. Personally I use a four stage reverse osmosis unit (as mentioned above) followed by fractional distillation for all of the water I use.
Residential fractional distillation unit:
http://www.amazon.com/s?ie=UTF8&keywords=water distillers&page=1&rh=i:aps,k:water distillers