I agree that serotonin syndrome is very rare, but the more recent data is clear that depression is not a "serotonin deficiency" syndrome. that theory is outdated. I think it's important that the OP discusses the symptoms with their doctor before buying several supplements. Vitamin deficiency could be an issue, and a simple blood test would help the doctor guide in which supplements are needed...

I also wouldn't advise people to take vitamin K without knowing whether or not they have a blood disorder, as vitamin K can affect blood thinners and could therefore be dangerous advice to dispense..