You haven't had them for that long and I'm sure you got wild caught. They're usually not well taken care of when you get them. That's another reason I'm against wild sales. It may take a while, but I think Lester is steering you right. They should have been seperated in the beginning for quarantine ideally, but right now I'd say they only reason to do so is if one is sick, or you're having trouble making sure they are equally feed.
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"A man that should call everything by it's right name, would hardly pass the streets without being knocked down as a common enemy." The Complete Works of George Savile, First Marquess of Halifax 1912,246