Anybody had problems with sponges

[molybdenumman]

I bought a blue sponge at the local fishstore on friday. I noticed the odd dead spot on it Sunday/Monday. Yesterday i went home from work and the sponge was half yellow. My hammer and frogspawn coral were shriveled up, my colt coral looked awful, my three rose bubble tips were shrunk up and were moving all over the place.

Is it possible for a sponge to cause a "wipeout" episode on a tank?

Is the best remedy to perform a large scale water change (20g new water into a 90g tank)?

Please let me know what you think.

DanTheMan