Firstly, i would do a 25% water change and then i would treat again, Is it a solid white bubble or cotton wool type growth ??
I don't want to step on any ones toes here but i know some guys that could help you out if you go to this link also,
I know this does not look right at all and if he hasn't swam into anything that could have caused the damage then it could be a bacterial problem, you will need to tell them what size tank you have, and the water state, ie: Nitrite, Ammonia, Ph and Nitrate.
Hope this helps, Good Luck