Fish in QT dying

[amy]

After reading through some of the posts on marine velvet and ick, I decided that I do not want to take any chances with my tank and will be quarantining everything prior to putting it in the display tank. I have a 10 gallon tank, bare bottom with a powerhead, a heater and some PVC for hiding. I got 2 new gobies on Sunday, so I added the copper to the water as per instructions on the bottle and dripped the fish to acclimate them.One of them died yesterday afternoon. I immediately tested all of the water parameters and everything was at 0, except for the copper which was at .4 (where I want it right?)
I woke up this morning to the other goby dead.
They only lasted 2 days. Have I done something wrong? Could it have been stress? I can't imagine they were both sick to begin with.
Any thoughts?