hm
I guess it comes down to the speed of the pathogen vs time till harvest. Realize though that this IS a plant pathogen that has infected your plants. It is only going to propagate, both onto other plants and through the vascular bundles of that plant.
my guess is a fungus, although bacteria can also cause this. either way...simply oxygenating the water wont work. at some point in the near future, you have to get rid of all the plants you have in that area, completely clean, COMPLETELY!!!! everything. get new nets, pump, hosing, etc, or get access to an autoclave and sterilize it all.
This is my advice, and a few things I remember from that plant pathology class a couple semesters ago. Just dont underestimate the ability of this stuff to spread, all the plants that are in the reservoir have likely been contaminated.