Stress or Sick?

[Clb33]

Hi all, I was curious what everyone thinks on my male Pelvicachromis Taeniatus "Moliwe” this has been going on for about a day and a half now. He has been breathing heavier and has stopped eating. All other fish in the tank are acting and eating normally. I have tried additives(garlic guard) to get him to eat and nothing has worked. He is in a 55 gal with 2 Angels, 1 Festivum, 1 keyhole cichlid, 1 zebra danio, a female Pelvicachromis Taeniatus "Moliwe”, and 4 bn plecos. I have done about a 30-40% water change tonight as well to see if that helps and moved him to a little hospital tank/fry tank that floats in the main tank to keep a closer eye on him.