Troubleshoot my paper mache!

So I am trying to make little paper mache ghosts. I am using only white tissue paper. My test ghost looked good after 24 hours. I popped the balloon and gently eased it out noticing that it was still a bit damp inside. I left it in my warm dry laundry area to finish drying. Now it has streaks on the inside that are kind of rust colored. And of course since it is white and thin they show from the outside. What happened?