Plants are struggling!

[Starry]

Tearing down the tank doesn't sound like a bad idea, but I know I wouldn't want to do it either. Herbicides can be pretty persistent though, so if things aren't looking up in a week or two, don't waste your time and money on it. For now, do LOTS of water changes. 60% twice isn't a lot at all, I would do 50% daily for at least a week or two. But your problem still wouldn't be the water, the herbicide is adsorbed to your substrate. Herbicides are notorious for their persistence. Good luck though, let us know what happens.

Edit: The KH change wouldn't have been a problem BTW. Also, how much of this herbicide did you add? And what exactly is it?

 

[Sumpin'fishy]

I added 1/4 tsp of "Greenlight Cut Vine and Stump Killer" -meant to kill the freshly cut stumps that are still green before you add the "Stump Remover", which is meant to jump-start the decay of the already-dead stump. I added 1/4 tsp at the beginning of the week (after water change) and then again at mid-week. That is all I added. And, as I've said before, it DID raise the nitrates!