Sounds like you have been reading the articles from a company that sells the substances you listed. Dendrite and axon growth is very slow. Each dendrite and axon may grow fast but the network of dendrites and axons take thousands of growth steps to make any difference.

I am not saying they don't help but it takes months and years for the connections/networks to develop into a properly functioning neural network. Plus, these networks need proper protection with myelin to transmit messages. The myelin is slow growing and matures slowly. Some believe that damaged myelin is more likely the problem with concussions.