I'm not sure honestly. I know there's more of the white than there was yesterday, but for all I know it just means it grew more. I didn't exactly measure or anything, you know? I guess all I can do in that case is watch him and see if it moves higher up the fin or not.
Like I said, he is looking better all the time, it would make sense for his fins to be growing. At least the stress coat can't hurt, and I'll have the salt around for later if it turns out I do need it.
Thank you so much for all your advice, by the way. My little fishy's recovery is largely thanks to you. :)