SICK OSCAR FISH EMERGENCY

I bought two albino oscar's about three weeks ago. they were healthy when i brought them home but within a week they stopped eating. I have them in a 50 gallon hexagon with a Whisper power filter a heater and some ornaments and fake plants. there are two bamboo shrimp and a dozen glass shrimp living with them. I have been doing weekly water changes and adding a drop or two of garlic extreme to get them to eat something.  last night when i got home one of the oscars was swimming in spirals. on of his fins looks injured and his dorsal fin is beat up and some bone of his fin is actually exposed. i did a 30 percent water change and changed my biobag. added some pimafix while the bag was out thinking maybe they have internal infections. the crazy swimmer was acting normal again for half the night then went back to spiraling. this morning he is doing laying on the bottom on his side and swimming totally upside down. can someone please help me i really love these fish