This happened to me twice within 2 months. It was absolutely horrible. Turns out it was that the town added chloramine to the water supply. It didn't have an effect on my smaller tanks, just my 265 with all my Haps. I started over and went to Mbuna. Now I have the itch for larger fish again. You'll get the itch, so if you don't need the money I would suggest to put it all in storage until the itch comes back.
Good luck.
Ted
Good luck.
Ted