Water parameters:
pH: 7
Nitrate: near 0
Amonia: near 0
Temperature: 83 - 84
One of my discus is losing its red color and turning yellowish. The image with green arrow is the before picture. I am noticing low appetite in the discus. I feed them frozen bloodworm and dry worm looking food. The checker discus in the image used to peek on it at beginning but that behavior improved. I change 25% of water every week. I am a novice fish keeper. This is my first aquarium. Any help would be appreciated. Thanks!