The white as near as I can determine by photo is Ich Fungus. Compare with online photos. It is Eradicated by Malachite Green Ich medicine. Remove your fish to hospital tank or fish bowl with aerater and sponge filter and administered proper dosage for water volume. Usually up to a 3 day treatment. As spores are carried in the water, even if healthy fish are infected, they might fight it off without treating the tank. More frequent water changes should be in order first. Treatment of tank with Ick medicine could compromise beneficial bacteria biological filter. Treat tank and fish with a slime coating. Monitor water toxin levels closely. Ammonia, Nitrate, Nitrites. As Ich is often present in a tank, healthy fish are usually unaffected. Wounded and stressed fish manifest symptoms. Can also be heightened by toxins in water. Also add a slime coating conditioner. A wounded, sick fish has lost portions of it's protective slime coating allowing bacterial and fungal infections to enter. Add elevated dosage of Prime or Safe conditioner/detoxifier with frequent water changes may resolve any Ich manifestations without main tank treatment with Malachite Green. If persistent case of Ich manifestations of Ich remains on fish in main tank then treat with 3 day course (or per instructions) of Malachite Green Ich Medicine. Best Wishes for your fish's recovery and resolvement of this problem! - Mont.- Might also consult trusted, knowledgeable local fish store professional.