Man sorry you lost that fish, it definitely had some nice coloration. What type of parasites caused the problem. Mine are refusing nls, but eating blood worms at the moment. Their feces looks normal and they are very active. I am going to soak some pellets in boyds today and see if that makes a difference, and then hopefully give them a few days of food soaked in 3% magnesium sulfate.
I believed mine had hexamita/spiro, he had white stringy feces and lost his appetite completely after a short while. I tried treating with Epsom salt soaked food first, then when he stopped eating I began injecting Epsom salts down his throat with a pipette. This did not prove effective for me in this case. I also tried metronidazole as a last ditch effort but I think he was too far gone at that point, and it didn't work.
I don't think my fish came from CoA with the parasites, as I got him at 3" and grew him to 6", which is when he got sick. I bought some ameca splendens which I believe had the hex, and he ate one of them. I treated the rest of the ameca's with Epsom salt soaked food which did cure them. Not sure why it didn't work for the lyonsi.
While I had him, he was really an awesome fish. Underrated in my opinion. Typical amphilophus behavior in a prettier (in my opinion) package. I think you will really enjoy these guys