Hello all! I've had some Celebes Rainbow fish for a while now. They're all happy, healthy, etc. Two of them (there are seven altogether) are changing in colour. They used to be clear with a gold-ish tinge to them like the rest, but now they're changing to a darker blue-grey. Sorry, no pics. They're too fast!
I've googled and found nothing on this. Is this normal? What does it mean?