Whoa! I thought it was just a time out until tempers subsided ...
he is growing livers in there again
WTF! What nutrients are being used? Any additives? This must not be. Suffer not the livers to live!
While I see no evidence the tub is the culprit, a new one costs ... $3? $5? Worth a shot.
Any reason he can't drop the H2O2 and move to tap water? Using Tap water (no H2O2) with GH FloraMicro and FloraBloom, I've never seen livers.
I'd suspect the Micro has fallen out of solution but, that would affect your garden as well. Still, the official fix for that is mix Micro with equal parts hot water and use at "double" strength.
What kind of water temps?