Broccoli, Chicken, Cheddar Soup

I sauteed olive oil, garlic, onions and mushrooms in a pan until onions were tender. I then combined cooked chicken (I just cooked 4 chicken tenders on the stove in a frying pan with olive oil), broccoli, cheddar cheese, low sodium chicken broth and onion mixture in crockpot. I then cooked it on high for 3 hours, adding cheddar cheese in the last 30 minutes. It's really good, but I still think there is too much sodium. I didn't add any seasonings to save on sodium. I think next time I'll attempt to make my own vegetable broth. Anybody ever done that before? Suggestions?