Hello and welcome,
First off, don't add anything else to your tank! You need to get some saltwater test kits, at least the basics : ammonia, nitrite, and nitrate. Read some of the "how to" threads on here, especially on cycling your tank. Are you using RO (reverse osmosis) water? And if your tank has only been running since Oct., it's WAY to early to add an anemone. I don't know what died first in your tank (I'm going to guess the anemone), but it caused a huge ammonia spike, which is extremely deadly to your tank inhabitants.
All I can recommend is to do lots of reading, and twice as much research! There's a ton of very useful information on this site. Many of these members have been doing this for years, they know there stuff.
Once again, welcome to the forum and keep us posted on your progress!!