I looked at his videos posted on YouTube and he’s tried multiple Cohabs that I would say didn’t work. That manueli looked pristine around January. It sucks to watch because so many people try so hard to get fish like this and would actually love the opportunity to grow them out. IMO it’s not really a cohab considering the condition of these fish. They're clearly picking each other off slowly. As far as constructive criticism goes;
Separate all the serras into individual tanks,
Remove cichlids if you want them to live and not be food for the reds,Start medicating all the fish that have been beat up.