Are you asking all that, to see if we agree?
Reef crystals should help in general. As stated, I wouldn't add anything like iodine without testing for it and dosing only as needed, which is usually nothing if you are doing enough water changes. It is possible to overdose iodine, it can actually cause things like shrimp to molt sooner than they should. It will help with the calcium.
You need to test for things that you dose. Blindly adding iodine, Ca
, etc. will cause imbalances and overdoses.