I age only 20 gallons of water and straight tap the rest 20-30 gallons of water .My tank is total of 55-60 gallons of water. I mix the hot tap water with the colder unheated aged water in the aging barrel during the process of refilling my tank (mix cold and hot while the pump is reffiling my tank )and it ends up the way I like it with a little practice .
Be careful of microbubbles during large WCs with unaged water because they can be more harmfull for discus than the PH swings if there are plenty of gasses in your tap water .
Be patient with regaining the lost appetite , because IME once discus loose appetite and white poops it's a long process to get it back to eating again(talking weeks) .in the past my discus started pecking on food even after the whole 2 week treatment was over .
And good luck for both of us