Black kuhli turning white?

[Bettas&Loaches]

I have had 5 kuhlis in my 20 gallon tank for over 4 months now, seemed really happy and healthy. One day I come home and notice the smallest kuhli's head is turning white. Nothing seems wrong, because it's still eating well and is very active. Any thoughts on why?

 

[SeanTrollope]

hi there and welcome.

okay so we are going to need a little more info on your tank before we can accurately answer this question. what are your water parameters. how big is your tank. what else is in the tank. so on and so fourth.