These are ACS line drawing characters. Putty does not support ACS line drawing in UTF-8 mode. For this reason (since tmux 1.4) tmux uses UTF-8 line drawing characters when UTF-8 is enabled. Make sure tmux knows the terminal supports UTF-8, either by using the -u flag (tmux -u new and tmux -u attach) or by setting LANG, LC_ALL, LC_CTYPE appropriately.
ps -f prints the command line, ps -C is searching by the command name. These are often the same, but they don't have to be.
In your setup if you tried
ps -o comm,cmd 4129
you will see the two fields. The command name is the first column with the command line being the second.
You could just run something like this in each window:
while :; do ssh $i tmux a; sleep 1; done
Or write a script that checks the windows periodically and uses respawn-pane or respawn-window to restart them if necessary.