Getting that temp up ASAP is critically important and may in fact be the bulk of your problem. Amazonian fish, for the most part, do not like anything below 74-76 degrees... and even that's pushing it. I've had heaters go out on occasion and what you describe is exactly what I saw. Fish lying on the bottom, not eating, eyes cloud up, scratching on the substrate. In addition to the problems that the low temps can cause directly, there are many secondary causes due to a lowered immune reaction such as bacterial infections or even parasites that the lowered temp could exacerbate.
Even though the fish have been OK up until now at the lower temps, the added stress of being moved around and placed in a foreign environment was enough to push them over the edge.
I'd get the temp up to a minimum of 78, I'd actually prefer 82 with these fish, and at least make sure they are eating. Once the fish stop eating it becomes exponentially more difficult to "cure them" whatever the ailment may be. You might find that the elevated temp solves everything.
I'd also perform a large water change regardless of your water parameters because as Jeff mentioned, it could be some sort of contaminant that is causing the gill membrane irritation. If directly after the water change the fish perk up substantially you might want to consider the contaminant idea very seriously.
Regarding treatment, I like to eliminate one possibility at a time as opposed to the shotgun treatment where you do everything at once. Raising the temp, performing a water change and adding 2-3 different chemicals/meds/treatments all at the same time makes it very difficult to know what exactly was the issue.
Good luck. Nothing worse than watching a prized specimen slowly wilt away.
