problem with doors

[spiderman2812]

I have 4 steel exterior doors that i've used in my studio. The walls seem to do a fine job but i think i'm going to have problems with the doors. Being that the doors are in place and the walls are painted does anyone have any ideas how i con stop leakage through the doors? They already have a rubber seal around them being that they're exterior doors. Oh yeah i also have 1 window i'll probably need to deal with.
Thanks!

 

[apl]

You could add really nice tight heavy storm doors.