were you measuring tds? what plant species were you keeping were you injecting c02?
give those drums a blast out with hydrogen peroxide
edit:after some thinking what substrate were you using, mine was ada and when the kh fell to 0 ph plummeted maybe if you had inert sand/gravel in your tank it would explain why nothing melted possibly your ph stayed around 7, the meltback could have been due to the ph reducing effects of the ada + 0 kh in my tank
Edited by Bombshocked, 17 October 2014 - 09:14 AM.