Although SCALES is second to none in the DC area, I think that they only quarantine marine fish.
How many people are willing to pay two times the cost for a fish to have them keep it in quarantine 3-4 weeks before selling it?
You're rolling the dice by introducing fish without quarantining...even when they have been "quarantined" at the LFS.
In short, it's your fault.
I've never been to Riverdale Pets, but if it's a stinking h*ellhole with bad customer service and sick animals, don't shop there. But don't complain that when you drop something from there into your system that there are disease issues..