Hi, i have an auratus and a socolofi in a 200L tank. theyv been there for 5 mounths and they are 2 years old. in the last few seeks the aurotus changed his color from yellow to almost white. Im afriad that this change is due to some kind of problem or disease.. they fighting often but not harming eachother and the socolofi is the stronger one. bot of them are active and have good appettite.and both of them initiate battles. when the aurtos does it he changing is color so the lower part of his body turns black. what do you think is the reason for the discoloration? thank you