I know somethings wrong

[Fisheyes]

;DAs I am retired I get to spend most of the day pampering my 6 discus and other fish.
Mornnings include 50%water changes on a 33 gal ,water testing and offering a variety of tasty delights through out the day fit for the KING of aquariums .
I feed in the morning blk worms noon tera flake and evenings blood worms as well as other tasty treats :P
I truly believe I have a problem but really do not know where to start to make it right. ???
These 6 disc are now aprox 3 in.nose to tail.Three are gold orange pandas and three are red turqoise. I have had them for 21 days now and I have been concerned about one of them since I got them .He always did hang back away from the others.

Changing color to brownish. Head down slightly Timid when he comes to eat and seems to back off when the other fish rush in to eat. He does eat blk worms but not as readily as the others . I tried seperating the tank in two but it made no difference as to his eating habits .
??? So where am I with this guy
He is timid
Hangs by himself and darkens up
Comes out to see me and flashes his colors --great
Eats very little (some blk worms)
certainly not as active as the others.

Chg.50%water daily
water specks- amonia 0- nitrite0 -ph 7.6-hi ph 7.8-Kh 71.6-gh 71.6 .
I present a varied diet 4or 5 times daily
I have now raised temp to 90 and added 2 table spoons salt per 10gal. Fish now breathing heavely so added airstone along with the sponge filter and aqua 300

I should add all fish have normall feses not stringy but brown and solid.
Where do I go now
Thanks for the help as usuall

[fcdiscus]

Just from the picture and your description, I would suspect a bout with gill flukes. Frank

[Fisheyes]

Thanks Frank
I have concidered that .
What would your treatment be .
Treat one or treat all 6in the 33 gal
thanks Ken

[fcdiscus]

I would do the whole tank with 1.5 ml per 10 gallons with Formalin, and a 50% WC after 5 or 6 hours. Repeat every other day for at least 3 treatments! HTH- Frank