lower the temp down to around 76-78, 84 can do permanent damage to gold fish as they live in colder temps. Ich isnt that big of a problem, the problem is what caused the fish to get ick aka "new tank syndrome". I'm guessing that the tank isnt cycled which in combination with being stressed from its new home is the cause of the ick.
If the tank isnt cycled buy some prime or safe. Safe is the same thing as prime but a ton more concentrated. Dosge till ammonia is gone testing every 24-48 hours and your gold fish should recover with bumped temp and a bit of salt. That should do the trick.
lowering the temp isn't gonna help with ich theyre fine in that temp warmer water will just mean more activity and bigger appetites with bigger and messier bio load.