Too much barley in vegetable soup
In my personal experience barley is often like lentils and rice in that it can "take over" a recipe if not used judiciously. Too much barley and your soup turns into stew. That happened to me recently.

I've recently been reading "Salt, Fat, Acid, Heat" by Samin Nosrat and besides it being an excellent primer (or refresher course) on how to learn to cook intuitively she talks about what you can add to various dishes to counteract various ingredients.

As barley is a starch the best you can do is dilute it, or thin it out a bit. You may need to add a fair bit of broth and more of your vegetal ingredients. Possibly to the point of doubling your recipe. It will depend on when you find the taste and texture to have gotten back to acceptable levels.