Hey everyone, I have five Tropheus duboisi and two of them are turning from a deep black to a lighter grey colour. On one the front half is the grey colour and the back half is the deep black. I think this one is the largest one out of the five. While another is a lighter black and this one is probably the second or third largest. These are the only two that are like this. Does anyone know why this has happened? Any help would be appreciated. Thanks.