I can use some advice and feedback, I made a medicated slurry

[Stroy15]

I changed my filter (replacing the carbon and fiber) last night and a white cloud came out of the filter outlet after some air went through it which I think was due to bacteria growing inside the tube.

Today I went to do a major water change and it stressed some kulli loaches out in part due to temporary lack of oxygen or because of wrong ph coming from my water change (I tried to lower to ph to 7 from my 7.5 water in my buckets but I think I over did it. I got a fresh bucket mix it up till I got close to the ph I wanted although I think it was too low. The tank measured 6.7 when I started the change.) I moved 15 gallons from my 47 gallon tank 

I made a medicated food slurry (using colu's instructions) using kanaplex because the kulli loaches seemed discolored with red gills (they were not happy about the water change and/or maybe they are inflicted with a condition. I saw this kulli loach poop with some air bubbles coming out with a long poop with a tinge white, but I have no reference for what it's (kulli loach poop) supposes to look like. I have read articles indicated that fish a mucus coating that is often white and does not always indicate disease or parasites.

Edit: I added 40 gallons worth of Malifix and a tablespoon of aquarium salt

I am looking out for suggestions on how I could have done this better and what might be wrong with the tank.

Ph 6.7-6.8

Kh 0-40

Gh 200

Ammonia 0.25 (I added a 1/4 teaspoon of fritz prime and nitrifying bacteria)

Nitrite 0

Nitrate 5-20

Temp 76

Edited September 6, 2022 by Stroy15

[Colu]

It's more than likely the 0.25 of ammonia That causing the cloudy water and the red gill's and discoloration of your loach what I would do is stop the medication and do is test daily and do daily water changes and add a double dose of prime to help detoxify any ammonia and add an extra air stone to increase levels of desloved oxygen till your ammonia constantly stay at zero

Edited September 6, 2022 by Colu