It certainly could be that he needs a higher dose, but there are a few other things that should be considered as well:
How long has he been taking the herbs? Some herbs need to be taken for a period of time before they have noticeable effects (i.e. Hawthorn takes like, a month before you start noticing anything)
Are you using any catalyst herbs with it? Echinacea is pretty mild and benefits greatly by adding Cayenne to it. Also, Black Pepper increases the efficacy of Tumeric by like 2,000-6,000%
How is he taking the herbs? Tinctures get absorbed rapidly into the body’s system, while capsules can take longer and sometimes negate different benefits of an herb entirely.
For bloating, I would try doing Fennel and Peppermint together as they both have good actions as Carminatives.