Fins turned white? Wow, that's definitely interesting. Is there any possibility that you may have gotten any chemicals or aerosols in the aquarium?
What I would honestly do is, strip the aquarium down to nothing. Let everything dry in the sun for one week. Then, I would fill the aquarium back up, and let it cycle once again. Where did you get the feeder fish from? What is the temperature of the aquarium? Is is possible that there's something wrong with the filter itself? Are you using the water conditioners, as directed?
What I would honestly do is, strip the aquarium down to nothing. Let everything dry in the sun for one week. Then, I would fill the aquarium back up, and let it cycle once again. Where did you get the feeder fish from? What is the temperature of the aquarium? Is is possible that there's something wrong with the filter itself? Are you using the water conditioners, as directed?