This is a tricky one. While yeast does contain glutamate, so do plenty of other foods with protein, like meat. The glutamate isn't the issue - it's when these proteins are hydrolyzed at high temperature, creating a different form of glutamate (a less healthy form).
I've read both sides, and I'm not convinced that yeast extract contains the unhealthy form of MSG - which is fundamentally, chemically different from glutamic acid. But I'm also not convinced that people who are very sensitive to MSG wouldn't have a reaction when exposed to this particular form.
We say nutritional yeast is okay for the Whole30, and I doubt that yeast extract is going to present a problem for 99.99% of folks doing the program. But for now, as Tom said, we'll encourage you to look for foods and products without these added ingredients, or better yet - just make your own chicken broth. However, I would see no need to start over because you ate some yeast extract in your soup.
More carbs is the only way I can keep my cycle on track when Whole30-ing. I have to make an effort to eat lots of starchy carbs (and find I have to add in a bit of rice to keep my cycle on track, too) or it takes a long hiatus. I know there are a lot of folks that will tell you the Whole30 isn't low carb, but that's how I tend to eat when I'm Whole30-ing so I really have to try to increase those carbs.