it good that he eating though.
Not sure what white is. Is it fuzzy? White can be fungus, just excess of slime coat, or external parasites.
Check on that white thing when you come home. It just my concern that you wrote that he is darting and a lot of time fish will dart if they have external parasites. So if you can take flashlight and shine on him and see if he has white spots on his body or if he looks like he sprinkled with salt , or if it looks like his body covered with a fine gold or rust mist.
I have a few IAL i can mail them to you.
Until we don't know what is white keep him on epsom salt,stress coat.