What\'s wrong with this fish?

For about a month, the end of my neon tetra's tail has developed a pale white patch. Yesterday I noticed him struggling to swim, as if he had a swim bladder issue and had become too buoyant (he couldn't stop floating upwards, and had to fight to stay deep enough.) I did a google search and found out that discolored patches and trouble swimming can be an indication of neon tetra disease. Today he's swimming normally again, but I noticed a smaller off-colored patch on one of my other tetras as well. I separated them out and started them on antibiotics, but I'm wondering if someone more familiar with NTD or false NTD (similar symptoms but responds to treatment, unlike NTD) can take a look at a picture of my afflicted tetra and tell me if it looks like he's suffering from either of these diseases (or something else entirely...)

Here's a link to a pic of him and the other tetra I noticed discoloration on:
http://i226.photobucket.com/albums/dd12/...
In real life the discoloration (right at the tip of his tail just in front of the tail fins) is a little less gray-looking and more whitish. You can't see the patch on the second tetra in this picture, but it's much less defined and I separated him out mostly as a precaution.

Does anybody know what is wrong?

Nothing to be concerned about, you may have fallen victim to the neon tetra disease but I don't know what it looks like. I know it is common in tetras hence the name..

Take him out of tank with other fish. I could be ich. I'm not sure. But that is a awsome picture of your cute little fishy.

I'm thinking fungus. or body fungus that really not a fungus but is caused by bacteia. You should seperate him in another tank.

Diagnosing fish diseases is very tricky. There are numerous causes that produce similar symptoms. Sometimes the problem is caused by water chemistry rather than disease. Below are links to sites that may help.

http://www.fishyfarmacy.com/diseases.htm...
http://fish.mongabay.com/diseases.htm