Fish losing scales.plz help?

well long story short. I found tank with two goldfish without a filter and maybe an inch of water. I "adopted them and put them in temporary tank while i cleaned the old tank(it was ful of alge and had who knows what in it) and now i put them back in the tank (20 gal) and put stress and zyme and everything but now one of them is losing his scales..Maybe because of stress