Hello Sir,
I am from Asansol West Bengal. I own a flowerhorn fish my tank size is 2ftx 1 ft x 1 ft without any other fish as its tankmate. I feed him with XO super red 3-4 pallets twice in 24 hours my heater is at 28 degrees Celsius and a sponge filter run by air pump and an overhead filter run by water pump I do a periodic water change and deworming with G-Probac and Energy booster once a week. 
The color of my fish got dark a couple of months ago and now its turning white near the lower fins and near its stomach. My fish is active and is feeding nicely. Please help me out.