I left and then came back, still thinking of your tank. I was going to have you fill out the ER questionnaire, but was second guessing that. No medication will be able to solve your overstocking problem. Once your fish are moved to a larger tank (40+ gallons for the goldfish alone), then we can look into if the fish are still ill. In the meantime, we can try to help you more, but you need to get a larger tank or move the fish back to the store. In a tank of this size, you will need to do daily water changes to keep it in check.

If you tell us your plan of action, we can get you through the period between now and then. I reread what you post and am sorry that you've lost fish. You lost them due to the overstocking. Medicine is not the answer here. Unless you change the size of the tank, etc.... then you are going to continue to lose fish.