New tmux sessions do not source bashrc file

Summary When I create a new tmux session, my prompt pulls from a default bash configuration and I have to manually run source ~/.bashrc for my customized prompt. Analysis I am using a RHEL 7 machine. I began noticing this behavior after a bash update a while back, but haven't gotten around to asking the question until now (and am not sure which update this began happening around). For example, I'v