You need to add H2O2 too that rez and kill the bacteria running rampid in there. Make the rez solution 3% H2O2 that should kill everything in there. You should also try to rinse the roots out, I bet they got root boogers on em.
O one other thing give them a second dose of the H2O2 in about 5 days just for good measure. And clean the hell out of that tank after this season and every other season after that that should help.