Sounds like serious water quality issues. Do you test the water for Ammonia and or nitrite levels. If so, is the tank in cycle ( this means you no longer can detect any ammonia or nitrite, only nitrate with a test kit)?
To remedy do 50% water changes daily and double dose your water conditioner IF it says you can on the instructions. Also, aquarium salt, follow directions on the box.

I agree with Woe. 50% water change daily, conditioner and some salt, just not too much. Goldies are strictly FW fish.

But also add MelaFix. It's perfectly safe and really does help combat fin rot and aid in tissue regeneration.

Some antibiotic such penicillin wouldn't hurt either. But you must remove the charcoal from your filter for either the MelaFix or an antibiotic to be of any benefit.

However, if you are doing water changes daily, the lack of either charcoal or amonia chips won't make any difference. Just run the filter with floss or a pad to trap solids and change or rinse it daily.

Goldies are about the easiest, yet conversely; difficult of all fish to keep in an aquarium. They are cold water fish, and as such need a lot more oxygen in their water than do tropicals, and for their body length, are far greater in total bulk than just about any other common aquarium fish, so need far more gallons per inch than the old and false standby, of a gallon per inch.

You are hopefully not keeping 2 of them in anything less than 10 - 20 very well filtered gallons?