There are some key attributes that you need to research on to determine brand health. Here they are:
Brand awareness (top of mind, aided)
Brand preference
Brand importance
Brand accessibility
Brand value (benefits divided by cost)
Brand differentiation or brand promise, and satisfaction against the brand promise
Check ownership of each important attributes in that category
Brand usage or brand used most often
Brand emotional connection, such as self expression or trust
Brand imagery or brand character
Do a perceptual map of important attributes, and how strong or weak your brand is in each category. If your brands are small, you will need to use deeper differentiation and more clutter breaking advertising style.