ill point out the obvious however, i successfully got 16 massive trees in 105 gallons of water eith zero airstones and zero air pumps, he has 2 plants in a few gallons of water with a massive airpump and 5 air stones.
this alone killed his plant. the rest of what i discussed with him in PM would have only ruined quality and yield.
heres a simple example i used.
humans have a ton of bacteria on them always (life is actually very disgusting and the more you learn the less human you start to feel).
"The bacteria cells in our body outnumber human cells 10 to 1, she says, but because they are much smaller than human cells, they account for only about 1 to 2 percent of our body mass—though they do make up about half of our body's waste."
http://www.popsci.com/science/article/2011-09/fyi-how-much-bacteria-do-people-carry-around
so say you look down at your arm, what you cant see is theres actually more bacteria than skin there lol but you dont get a rash unless that specific bacteria is allowed to grow above a certain population number. this could happen by not washing and letting it reproduce, or a weakened immune system that cant fight it off.
thats what happened to his roots. and eventhorizen you even pointed out the root rot days ago but he slightly shrugged it off. there is always root rot causing pathogens in the air and water, but they are under a population number to do any harm. his air pump was shoving massive amounts of the pathogen from the air into his water and even with his cold water the roots couldnt fight it off. plus my hypothesis is the cold water was also hurting the root health which was making it even more difficult to fight off root rot just like a weakened immune system on a person