it looks like there is algae choking the roots of your plants and eating all the delicious nutrients.

your reservoir needs to be light-proof, buy a roll of metal tape from home depot (should be near the ducting) and tape up every inch of your res until it is PITCH BLACK inside, even (especially) the top, anywhere you can see blue, needs to be taped.

I've tried duct tape, spray paint, black plastic.. the metal tape works by far the best, and it keeps it insulated (probably).

should solve the pesky algae problem... also throw in a few mls of that Hydrogen Peroxide daily to kill algae while you procrastinate