Planted Tank Guru
Join Date: Jun 2004
Location: Baton Rouge, LA
If I had to venture a guess, it would be that after killing all the bacteria, the contents of your substrate are now an anaerobic, rotting, toxic mess.
I'd gravel vac. Thoroughly and repeatedly, until the water runs clear. I did this when I intentionally nuked a tank with a whole bottle of H2O2, and had no problems. Hope you're not using dirt!
Sorry, no plants to sell at the moment. Have already promised my clippings for about the next two months to some local planted tank enthusiasts.