Large White Spot, Don't Think It Is Ich....help!

So, my husband changed food on his tank but didn't tell me.  I think I overfed them for a few days --- two fish died.  However, a third hasn't been eating and is hanging out at the top of the tank swimming towards the filter.  He has done this for days.  Watching him yesterday, I noticed a huge white spot on one side (it is about half inch long). We have two other large gold gouramis and a large black angel. 

Had to get the video off my phone.  Here it looks more like a burn, but to the naked eye it looks white.  Any ideas or suggestion would be great.  Sorry about the play sign, I had to take a screen shot to get the image. 

What size is the tank and how long have you had it for?

Iy is 55 galloon. We have had it since 05, but we have moved twice with it. The most recent move was in January of 2010.last year we had a lot of difficulties keeping the water balanced, and have all new fish. We haven't added any new fish in about 6 months. Currently, we only have the four fish.

Any ideas?

I the picture is not clear at all but from what you are saying I think it could be a fungus add salt touch your tank just in case holding thumbs