Hello. After having my new discus in quarantine for a few weeks, I added my hero discus in with them. After a few days, he is sitting at the bottom of the tank with clamped fins. He shows interest in food, but won’t eat. He is breathing hard and his gills are flared. His poop is normal. I do a 50% water change daily. The new discus are doing great. Any suggestions on how to proceed? Thank you.