I tried taking out the barbs and putting them into a 5 gallon holding tank where I medicated them four days straight just to be sure there was no disease. After they were done I put them back into the 20 gallon tank with the tetras. Needless to say they started loosing color so back into the 5 gallon tank they all went. After doing a 25 percent water change I took out all other fish and put them into the 5 gallon water tank and put all of the barbs into the 20 gallon with the 2 cories. All of the color came back and stayed back. They are all acting normal for the moment. I'm just guessing to say maybe the Barbs didn't like the Tetras in the same living space. The tetras float in the middle of the tank and that’s where the barbs like to swim. Come to think of it, this seems to have started happening after I introduced the 6 Neon Tetras. Maybe that’s the answer I have been looking for. By the way the Tetras like floating in their new 5 gallon tank. I left a picture on my avatar so you could see.