Hey there zantettsuken,
It ALMOST looks like you might have some foreign material inside your blade. I had a small cobweb in one of mine once, and it really showed up.
Just check your blade for crap...that'd be a quick fix.
The film inside is Mylar. That means it has a metal coating of sorts, and is in fact susceptible to heat and humidity - not kidding.
Stand them upright in a cool, dry place overnight. The film might straighten out.
A final solution would be to get a long piece of dowel or something, and flatten it out by hand. BE CAREFUL if you do that. Crimp or tear that film, and it's game over for that blade.
Lastly, I do recommend having a blade for dueling (that you don't mind seeing scuffed up and a bit beat), and another (potentially mid grade) for display.
Hope this helps.