While one pair breeds, the other refuses food. If the only signs of illness are refusing food, losing weight and hiding, what does that mean?
Probably so many potential reasons it’s impossible to answer the question, but I want to try and get them eating, so I ask it anyway.
Also, if the unpaired fins of the male are mostly black with blue-green edging this is probably not actually opallios, the red color near the iridescence is pretty obvious if it’s opallios? I have no good camera at the moment.