I honestly don't know what to make of that. Perhaps someone else can comment but I strongly suspect they are not compatible with each other and will have to kept separate. See if there's improvement in Gonzo if they put separate rooms. Sounds like an extreme case of aggressive chinchilla. Not eating can also be a symptom of other health disorders. Considering the change is sudden and unexplained you may want to have a vet exam and make sure it is not a health issue and try to rule out things like tooth problems. What is their diet?
it is tough. a relative of mine has agreed to adopt Rizzo as Gonzo and I were perfectly fine on our own and i have alot of time to spare to spend with him, and my relative has a lot of time for Rizzo too.
i have considered this, he has started to eat better than before.
i give him his pellets at 6.30 pm every night and he has hay too. barely any treats and if, on the occasion, i do give him a treat it is a plain shreddie or a raisin
i have checked any physical signs of illness and all seems okay. his weight is still the same and he looks physically well, his teeth are perfectly short enough since he has plenty of wood and mineral stones to grind down his teeth.
i may take him for a check up. and i will see if his behaviour does change when my relative comes to collect Rizzo (she only lives down the road so i will still see him!)
thank you so much for your help