Had to have a disaster sooner or later!! Help!

[Slick Fork]

I'll second the call for new carbon and water changes. Also, with the water changes I see that your hydrometer and refractometer are a long ways apart. Don't necessarily take the refractometer as being dead on. Use 1 or the other and match the water change water with the same. So if you use the refractometer to check the tank, don't use the hydrometer to check the new water. Worry about bringing everything down later but for now more and drastic change will not be a good thing.

Pull the sponge and toss it, my immediate hunch is something got onto the sponge if you just cleaned it last night.