Just saw your post. As said before, the fin rot/whatever it may be is possibly due to bacteria in the water eating at the fins(fin rot) or just stress. You can go to your local pet store and they usually have stress remover bottles for like 3 dollars. They also have certain medications for fin rot in bottles you add to the water in the tank for fin rot.
Signs of fin rot:
white tips on the edge of fins
fins starting to dissolve from the edges... it looks a bit like dried paint that's been exposed to paint thinner
holes in fins, or fins starting to appear thinner than usual
symptoms may develop quickly, or slowly progress over a few days.
the fins make start to look stiff
slimy areas near the top of the fins that seem to eat away at the fins over time
IF FIN ROT:
Immediately do an 80% water change with water that has been treated with a water conditioner and is the same temperature as the old water in the tank. Change 80% of the water again two days later. Be sure to really stir up the gravel and get the tank clean.
If you have plastic plants, submerge them in a 10% bleach solution, scrub them clean and run them under clean water for a few minutes. Even live plants would benefit from a gentle scrub and being rinsed in clean water. Consider removing all the gravel until the fin rot is under control. You might also want to net your fish and put him in a safe place, as the last thing he needs right now is to be "home" during this violent housecleaning. If your fish has just started showing the smallest symptoms of fin rot, you might get away with just doing a major cleanup of its tank.
Get some mercurochrome - the kind of old medicine cabinet remedy some of us older folks used to put on cuts and sores. Put 3-5 drops of mercurochrome in a tiny dish, then add the same number drops of water. In other words, dilute the mercurochrome by 50% with regular tap water. Get a few qtips. Now net your fish and dab the mercurochrome-moistened qtips on all the affected parts of his fins or anywhere else that looks burned. Just leave his eyes alone - they can't handle the treatment. Your fish will be OK out of water for a minute or so - any more than 90 seconds is too long, so be sure to have everything you need ready to go. After you're done, release the fish back into the water.
Doing the mercurochrome treatment after you've isolated your fish in a temporary container and thoroughly cleaned out the tank seems to work well. That way there's less chasing him around with the net, and he gets released into nice clean water, instead of being re-exposed to that old acid broth. Repeat the mercurochrome treatment again in 3-4 days if necessary.
Thats it! :) or the old epsom salt bath or even aquarium salt or table salt trick :) hope this helps
Increase the temperature of the tank (slowly please... use a proper aquarium heater) to 80-82 degrees.