Note that the JupyterLab terminal does not start its terminals as login shells, but as interactive non-login shells (see this explanation of the difference). This means that .bash_profile is not executed for you in the JupyterLab terminal.
Is it possible that some of the configuration that you expect is being loaded by .bash_profile? You can test that by running source ~/.bash_profile in the JupyterLab terminal; if that fixes the problem, then you’ll need to rethink how you lay out your relationship between .bashrc and .bash_profile so that you get the behavior you want in all non-login shells…