I purchased one red and yellowish gourami (forgot the actual name of it) from petsmart about a week ago. Since being in my established 25 gal
. community tank it has began to turn a greyish color on the top of its head and the bottom of its belly. It is not spotty or anything, it is more like he is slowly losing his color and it is spreading. Any idea what might be causing this? What can i do?