Hi Alpha, It sounds like your conditions are perfect so I would think it has something to do with either the chiller or the ph down you added directly to the res. You have to dilute it a bit(1 litre of water) it takes several hrs to blend in with the nute solution so it is very possible that they got a concentrated dose to the roots, it also has a bad effect on the nutes when you mix ph down directly to the res. did you notice any white clouds when you added the drops? Did you run a high concentration of h2o2 water through the chiller before you hooked it up? How long did it sit before you got it? There could of been mold or something in it.Get rid of the foil and pick up some panda film, cut your circles with a slit and place them white side up, this will reflect the light evenly and stop any algea from building up.the foil is a no no it will cause hotspots 100%.I personally have never used AN's base nutes before but ive read alot of mixed reviews about it so I stay away from it.up until my current grow I was a Gh flora guy, this round I switched to BPN's High Yield System and so far its hands down the most stable stuff Ive ever used. Shipping for me was $200 for the kit but the kit was only $140 for a total of $340. On average with Gh flora and all the addatives I used before each round was costing me well over $400 so even with shipping to Canada BPN is cheaper and so far imo better.Personally I would take the girls out of the system, dump a ton of h2o2 into the res and run it for a good hr. Drain everything and then dry everything to make sure you got all the h2o2 out of there and start over with a 1/4 strength solution for a bit and see what happens.You mentioned in your intro that you feel soil is more forgiving than hydro. I have to disagree with you there especially if your going organic, once the soils mixed you cant get the nutes out, with hydro its as simple as adding more water to dilute the solution.For something like this to happen this quickly it has to be caused by one of the recent changes you made.If your thermo is off and the water is colder than you think that could also cause problems quickly, I hope you figure it out im kinda stumped on this one. Im subbed up and will stop by from time to time to see how things are going.