Agreed with this post^^^
Dosing when not needed is very dangerous. Dosing iodine is never recommended at all. A mantis shrimp does not consume calcium, magnesium or iodine so there is no need to replace it. Those elements are all in a good salt mix to begin with and adding more causes precipitation and bad water chemistry. Dosing anything at all would likely only need to be done in a tank with stony corals and clams.
If she's still alive stop messing with the tank unless you are doing water tests and then only do it to make 100% sure your water parameters are good. Dosing, water changes and changing the light schedule only causes more stress. Anything that needs to be done to a tank should be done while the mantis is not molting. During a molt isn't a good time to be figuring out what's wrong with the tank.