Let's start with some basics about your tank.
How long has it been set up and running?
What is your lighting set up (bulb type(s) and wattage)?
What is your filtration set up (cannister, protein skimmer, wet/dry)?
Do you have a sump?
What else is in your tank?
What livestock do you have?
Do you do partial water changes, and how much and how often if you do?
Why are you adding Calcium, Iodine and trace elements to the tank?
Do you have a test kit for everything that you are adding?
Can you post the current levels for Calcium, Magnesium, Alkalinity, normal daytime pH, Iodine?
The answers to those questions will help people here give you good advice.
Also, where are you located. Someone might know of a great nearby lfs
. I agree on the choice of liveaquaria and saltwaterfish as well as a few others depending on what you are looking for.