Probably a water quality issue. I'd stay on some 4g (or just a
HD bucket worth) water changes every other day for a week and then back off until you get back to normal. See if you can scrape out the algae (meaning don't just rub it off, but get it out of the tank). Thoroughly rinse the sponge because it's undoubtedly chock full of gunk. Leave the light off for a few days, too. The fish don't need it and corals can generally tolerate a couple days of no light as well. You could turn the light off and cover the tank with a big towel for 2 or 3 days to kill the algae during the water change cycle.
Did they overfeed, too, or simply leave the light on forever? Do you have a
skimmer running?
You should get a timer from
HD or Lowes to control the lights.
