Add some FXAIX in my brokerage?

Hi all. This is where I’m currently setting. 401k in a targeted date fund. Roth is 100% FXAIX, HSA FXAIX, just opened my brokerage account and as of now is 100% VTI. Should I keep buying VTI in the brokerage, or add a percentage of S&P in this as well? Or is there another fund anyone suggests to maybe diversify a little more. The majority of my savings will be going in to this brokerage account throughout the rest of the year. Thanks!