Duplicate paths in the $ PATH environment variable

I have noticed that the paths I add to $PATH in my .bashrc appear duplicates when I open session in tmux (terminal multiplexer):

export PATH=$HOME/miniconda3/bin:$PATH
export PATH=$PATH:$HOME/Devel/bin

If I print $PATH in a session of tmux it appears as follows:

/home/alejandro/miniconda3/bin:/home/alejandro/miniconda3/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/home/alejandro/Devel/bin:/home/alejandro/Devel/bin

Out of tmux it appears normal:

/home/alejandro/miniconda3/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/home/alejandro/Devel/bin

I suspect it has to do with the first line of my .bash_profile :

if [[ -f ~/.bashrc ]]; then . ~/.bashrc; fi

If I comment on this line (which I do not quite understand what its function is), $PATH appears correct inside and outside the tmux session, except that I lose script% custom bash-git-prompt inside of the tmux session. Apparently tmux accesses the bash-git-prompt script by .bash_profile .

So far the solution I found was:

• comment the first line of bash_profile ;
• Copy the lines from .bashrc to bash-git-prompt script within .bash_profile (now those lines are in both files).

As a result, $PATH appears correctly inside and outside the session of tmux and the same thing with the prompt.

My question is whether it's right or is there a better way to do it.

Edited:

.bash_profile

.bashrc