Why am I feeling tired since STARTING to take vitamins?

I have gotten back to working out religiously for the past 4 months. I decided to start taking some vitamins. I am taking Ultimate Man multivitamin from The Vitamin Shop. I am also taking flax seed oil and fish oil. Since I have started taking these every morning, I just feel run down. I do 45 minutes of elliptical every evening and lift weights 5 days a week. I have changed nothing in my routine except the addition of these supplements. Does this even make sense? Nothing in my environment has really changed. Any ideas on what could be going on? Is this a stress thing that I may just not be aware of? And, if it is, wouldn't the vitamins help keep me energized? Thanks for any ideas you can give me.