If you medicated your tank this is a waste of time.
Ick is killing your fish, the medication is useless, petco is the same.
Get your fish (and only fish) out of your DT and into QT.
Nothing fancy, tank, pail, whatever, heater, sponge filter, hiding place...no live rock, we are nit cycling this tank, daily water changes and vacuuming up uneaten food will keep ammonia from building.
Treat your fish:
Pick a treatment. Cupramine can be quite successful but is hard on delicates like tangs. Hypo works great but you must keep water at 1.009 until at least 21 days after the last spot is gone. You can bring down salinity fast over two days but going back up must be real slow, .002 max per day.
Have a read of the stickys fir more details of treatment.
Treat your DT:
This is the easier part. Continue to run your DT as normal, (but without fish) everything else stays....run for 72 DAYS this way and Ick will by gone.
By this time, any fish you saved can go back. This works every time.