Fishsmurf is mostly right. But it is hard to know until you say what medication(s) you are using.
I'm puzzled at the malachite green AND copper ... that suggests you are combining medications, not a good idea. You are probably correct that the meds along with the ick killed your clown loaches. I know -- I have lost a boatload of them until I put my UV in. However, they are savable.
First, finish treating your tank. If you are combining meds or using a copper med that is not Aquarisol, then what you need to do is leave the carbon in 4-6 hrs and do your water change. Then I'd get a medication that will combat the ick but not overly stress your fish. Since none of your fish are showing signs, what I would do is put the temp up slowly, but maybe only to 82 or so unless you have a way to increase oxygenation as well. Then I'd treat with a mild anti-ick formula for 4 days as long as no white spots are visible on any fish. If you find any, then you have to go untill they are all gone then a few days extra.
There are many mild meds. I prefer Aquarisol as I've had the best success and have not lost any fish to it. Clear Ick by Aquatronics is another good choice. I'd avoid m. green and formalin as long as no fish are showing ick signs. If they do show spots, then Ridich + is a good bet, or Quick Cure if you have no plecos or scaleless left in there.
Wait a good 3 weeks before trying clown loaches. When you get them, buy the fattest (not necessarily the biggest ... you can get small ones, but be sure they are plump) you can find. Inspect carefully for ANY signs of ick before taking them home. Then, acclimate slowly and when you add them to the tank treat the tank with Aquarisol for 2-3 days after adding them, as a preventative.
This method has worked for me. Of course, other parasites can doom clown loaches too, as can not eating, a condition that is wasting one of mine away right now ... hasn't eaten, to my eye, once since I added him a month and a half ago... Not too much you can do about that. These are sensitive fish and if they freak out there isn't a lot of hope, at least that is my observation.