Can you provide us with any pictures? If not than answer the following questions as detailed as possible.
1. Are they eating?
2. What is the rating on the filter?
3. Are they breathing readily, heavily?
4. How many Goldfishes are in the tank?
5. Were they in the tank during the water change?
A. If not then how long did you wait before adding them in after you added chlorine remover?
6. What is the condition of the water (water parameters)?
7. What is the “thing” that is hanging (take a closer look)?
8. When did your fish start acting unusual (after being fed, after water change)?
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It sounds like they have a fungal infection. Mardel Maracide works well, but it will change the silicon (aquarium glue) in your tank blue. I have forewarned you about the side effect of the medication, of course there are others out there that you can try!
Have a look at the site below.
Identifying Possible Diseases.
I wish you the best of luck!