Sorry can't help you with this one. One of the chalices I bought from my LFS slowly started bleaching too (I started it about 2/3 of the way down the tank, and it came from dim light, so I figured it'd be okay). So then I moved it to the very bottom -- and the bleaching continued. So then I moved it to the very top, and the bleaching seems to have slowed down. It's hard to fix the problem, because it can be from either too much light or too little light.