so recently one of my discus hasnt been eating.also he isnt very active either.he looks perfectly fine his top fin isnt clamped down other fins are perfectly intact. the only time he really gets moving is when he chases the bigger discus away from my smaller discus.its a 45 gallon tank,with 3 four inch discus and one 3 inch, temp is 84, no ammonia ,no nitrite , barely any nitrate,and the ph is 6.0 . now my question is im getting ready to move them into my 75 gallon tank its been cycled and everything its had other fish for 2 years in there its ready to go just need the temp to stabilize. should i move only the one who isnt eating into the 75 and wait for him to start eating to move the others or leave him alone in the 45 and move the others?