Honey gourami sick help!

[PikaBu]

Help! My favorite honey gourami has fallen ill with something.
At first I noticed he was fading but I read it was normal for honey gouramis to change color as long as he's eatting which he was.
Then after a while he was eating less and is sluggish at the bottom of the tank.
Today I've noticed that he has slightly risen scales as well as a weird body shape as seen in the picture.
When he started to eat less I tested my water with the api master test kit and everything was low and looking normal.
I still did a water change after that but he seems to do better one day (acting like he used to pecking away at things) but the next day he would be at the bottom again. Help please

I have a 36 gallon bow front with an aquaclear 70 as well as a ehiem 250/2213. I do weekly water changes and a deep clean of the filters once a month.
In the tank there's another honey gourami that is the dominant one, 7 harlequins, 5 rummy nose tetras, 2 bolivian rams, 3 cories, and 5 gold barbs

 

[coralbandit]

The risen scales are called pineconing . They are usually a sign of some internal bacterial infection. Some call it dropsy but that is a name of the symptom. The swelling is from organ damage and improper function of the liver or kidney I believe.
It is possible the other gourami caused this but whether or not the infection can spread.
I would remove the fish for the others safety. In most cases once you see the symptoms the damage done internally is to far along to be cured.