Interesting. Well, calcium hydroxide is very caustic, and has a pH of about 12-13. I wouldnt be suprosed if it killed everything it touched in a marine tank. Things you should check upon repeat experiments would be pH and calcium. Before and after application. Also check out alkalinity. I have a feeling they are roller coastering around causing a calcium imbalance.
I am experimenting with my own homemade mixture. Should be available soon!