You upset your intestinal flora/fauna. Taking the two herbs together at once and on an empty stomach, especially if you haven't tasted them before, means your gut bacteria got a full-force dose of the herbs. Many herbs act as powerful alkaloids, and that usually disrupts the sort of gut colonies that like the usual western-standard diet of meat and carbs.
Herbs are best taken at 1/8-1/4 the reccommended adult dose (per day) when you first get them to test your personal reaction to them.
Herbs are to be treated as medicines, and rightfully so! Treat 'em with respect and they will be your best friends.
It is wise to have an adsorbant like activated charcoal powder around for absorbing dieoff toxins for when you are on cleanses or trying new herbs. The tiredness, gas, bloating and grumpiness are all dieoff symptoms. Most of the bacteria in the gut produce mood-altering substances, and they WILL LET YOU KNOW with minor to strong agony when they are unhappy! ... Just as much as they produce trippy-happy substances when you eat what they like.